SEARCH · Search PubMed

Results for “Profilins”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1991

Analysis of cDNA clones for Acanthamoeba profilin-I and profilin-II shows end to end homology with vertebrate profilins and a small family of profilin genes.

We have cloned and sequenced full length cDNAs for Acanthamoeba profilin-I and profilin-II. The genes and the encoded proteins are nearly identical except for the region between bp 121 and 210 where 35% of the nucleotides and 47% of amino acids differ. Most of these substitutions are conservative, although three of them are responsible for the differences in the isoelectric points of the isoforms [Kaiser et al., Cell Biol., 102:221-226, 1986]. The DNA sequence revealed six corrections in the previously published protein sequence of profilin-I [Ampe et al., J. Biol. Chem. 260:834-840, 1985] and for the first time resolved the ambiguities at the five positions where profilin-IA and -IB differ. The DNA sequence of profilin-II also allowed us to make two corrections in the protein sequence [Ampe et al., FEBS Lett. 228:17-21, 1988a]. Probes prepared from the cDNAs revealed 1 profilin-IA gene, one strongly cross-hybridizing profilin-I gene and one strongly reacting profilin-II gene on Southern blots of Acanthamoeba DNA. Weaker reactions with other genomic DNA fragments leave open the possibility of one additional gene each for profilin-I and profilin-II. Four different profilin RNAs were resolved on Northern blots. It possible to align the sequences of the three Acanthamoeba profilins with the sequences of nine other profilins from five different phyla. There are only two invariant residues in these profilin sequences, but many pairwise identities and conservative substitutions that indicate considerable divergence of this family of proteins from its ancestral precursor.

Acanthamoeba↗

PubMed1996

Arabidopsis profilins are functionally similar to yeast profilins: identification of a vascular bundle-specific profilin and a pollen-specific profilin.

Four members of the Arabidopsis profilin (pfn) multigene family have been cloned, sequenced and analyzed. By RNA gel blot analysis it has been shown that these four genes fall into two groups: one group (pfn1 and pfn2) is expressed in all organs of the plant and the other group (pfn3 and pfn4) in floral tissues only. Based on amino acid sequence alignment Arabidopsis profilins can be divided into the same two groups: PFN1 and PFN2 are 89% identical and PFN3 and PFN4 are 91% identical. Between these two groups they are 71-75% identical. The Arabidopsis profilins bind poly-L-proline and can complement both the Saccharomyces cerevisiae profilin deletion mutant and the Schizosaccharomyces pombe cdc3-124/profilin mutation, showing that the plant profilins are functionally similar to yeast profilins despite the low amino acid sequence homology. Analysis of pfn promoter-GUS fusion genes in transgenic Arabidopsis shows that pfn2 is specifically expressed in the vascular bundles of roots, hypocotyls, cotyledons, leaves, sepals, petals, stamen filaments and stalks of developing seeds, whereas expression of pfn4 is restricted to mature and germinating pollen grains.

Amino Acid Sequence↗

PubMed2001

Cross-reactivity within the profilin panallergen family investigated by comparison of recombinant profilins from pear (Pyr c 4), cherry (Pru av 4) and celery (Api g 4) with birch pollen profilin Bet v 2.

Profilin is a panallergen which is recognised by IgE from about 20% of birch pollen- and plant food-allergic patients. Little is known about epitope diversity among these homologous proteins, and about the correlation between IgE-cross-reactivity and allergenic reactivity. Plant food profilins from pear (Pyr c 4) and cherry (Pru av 4) were cloned by polymerase chain reaction and produced in Escherichia coli BL21. The profilins were purified as non-fusion proteins by affinity chromatography on poly-(L-proline)-Sepharose and characterized by immunoblotting, IgE-inhibition experiments and histamine release assays. The coding regions of the cDNA of pear and cherry profilin were identified as a 393 bp open reading frame. The deduced amino acid sequences showed high identities with birch pollen profilin Bet v 2 (76-83%) and other allergenic plant profilins. Pyr c 4 and Pru av 4 were investigated for their immunological properties in comparison with profilins from celery (Api g 4) and birch pollen (Bet v 2). Fourty-three of 49 patients (88%), preselected for an IgE-reactivity with Bet v 2 showed specific IgE-antibodies to the recombinant pear protein, 92% of the sera were positive with the recombinant cherry allergen and 80% of the sera were reactive with the celery protein. Inhibition experiments showed a strong cross-reactivity of IgE with profilins from plant food and birch pollen. However, IgE binding profiles also indicated the presence of epitope differences among related profilins. All investigated profilins, Pyr c 4, Pru av 4, Api g 4 and Bet v 2, presented almost identical allergenic properties in cellular mediator release tests. Therefore, cross-reactivities between related profilins may explain pollen-related allergy to food in a minority of patients. The nucleotide sequences reported have been submitted to the Genbank database under accession numbers AF129424 (Pyr c 4) and AF129425 (Pru av 4).

Allergens↗

PubMed1997

Effects of profilin-annexin I association on some properties of both profilin and annexin I: modification of the inhibitory activity of profilin on actin polymerization and inhibition of the self-association of annexin I and its interactions with liposomes.

We have previously shown that annexin I, a member of a family of calcium-dependent phospholipid and membrane binding proteins, interacts with profilin with high specificity and affinity. This finding further suggests that annexin I is involved through profilin in the regulation of membrane-cytoskeleton organization. We have investigated the consequences of a complex formed by these two proteins on the functions of both profilin and annexin I. Annexin I is able to modify the inhibitory effect of profilin on actin polymerization. This action is partial and the mechanism involved appears to be complex. On the other hand, the association between annexin I and profilin is sufficiently strong to inhibit the self-association of annexin I. The binding capacity of annexin I to liposomes containing phosphatidylserine, which mimics annexin I binding to membranes, is also decreased by profilin. This binding is nevertheless restored when phosphatidylinositol 4,5-biphosphate (PtdInsP2) is included in the liposomes. Finally, the capacity of annexin I to aggregate liposomes is also modified. It is worthwhile mentioning that the liposomes-binding and liposomes-aggregating activities of annexin I are independently regulated. The cell localization and functions of annexin I and profilin suggest that interaction between these two proteins may be directly implicated in the regulation of membrane-cytoskeleton. The phospholipid composition of membranes may be one of the modulating factors.

Actins↗

PubMed2000

Cloning of the minor allergen Api g 4 profilin from celery (Apium graveolens) and its cross-reactivity with birch pollen profilin Bet v 2.

BACKGROUND: Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen- and plant food-allergic patients. A subgroup of celery-allergic patients shows IgE-reactivity with this minor allergen. To investigate the IgE-binding potential and cross-reactivity of celery profilin at the molecular level, this study was aimed at the cloning and immunological characterization of this allergen. OBJECTIVES: Cloning, expression and purification of profilin from celery tuber to characterize its immunological properties and its cross-reactivity with birch pollen profilin. METHODS: Cloning of celery profilin was performed by polymerase chain reaction using degenerated primers and a 5'RACE method for the identification of the unknown 5'-end of the cDNA. Expression was carried out in Escherichia coli BL21 (DE3) using a modified vector pET-30a. The recombinant profilin was purified by affinity chromatography on poly L-proline coupled to sepharose. Immunological characterization was performed by immunoblotting, EAST and IgE-inhibition experiments. RESULTS: The coding region of the cDNA of celery profilin was identified as a 399-bp open reading frame, coding for a protein of 133 amino acids with a calculated molecular weight of 14.3 kDa. The deduced amino acid sequence of the corresponding protein showed high identity with other plant profilins (71-82%) recently described as allergens. Celery profilin was isolated as highly pure nonfusion protein. The IgE-reactivity of celery profilin was similar to that of natural protein. Seven of 17 celery-allergic patients tested presented specific IgE-antibodies to the recombinant protein tested by immunoblotting. Inhibition experiments showed high cross-reactivity of IgE with both profilins from celery and birch pollen. Moreover, the biological activity of recombinant celery profilin was demonstrated by a histamine release assay. CONCLUSIONS: Celery profilin is an important allergenic compound in celery and shows high homology to birch pollen profilin, Bet v 2. According to the revised IUIS allergen nomenclature, we suggest naming the celery profilin Api g 4. In addition to the cross-reacting major allergens Api g 1 and Bet v 1, birch pollinosis and associated allergies to celery can therefore additionally be explained by the cross-reactivity between homologous profilins. Moreover, recombinant Api g 4 may be used for target-specific diagnosis and structural analyses.

Allergens↗

PubMed1994

cDNA cloning and expression of timothy grass (Phleum pratense) pollen profilin in Escherichia coli: comparison with birch pollen profilin.

Profilin, an actin-binding protein, was previously described as a ubiquitous allergen which is responsible for cross-reactivities in about 20% of pollen and food allergic patients. A complete cDNA clone coding for timothy grass (Phelum pratense) pollen profilin was isolated using allergic patients IgE. The deduced amino acid sequence of timothy grass profilin shares a sequence identity of 79% with birch profilin and other plant profilins and a lower average sequence identity of 35% with other eukaryotic profilins. The high degree of homology among different plant profilins at the DNA and protein level explains the extensive cross-reactivities observed in profilin allergic patients. Recombinant timothy grass pollen profilin was expressed in Escherichia coli as a beta-galactosidase fusion protein and shown to bind IgE from profilin allergic patients similar to recombinant birch profilin. Slight differences regarding the IgE-binding capacity of birch and timothy grass profilin indicate that not all IgE-epitopes of the two profilins are conserved. It is speculated that profilin allergic patients were initially sensitized against a certain profilin and then cross-react with the homologous proteins.

Allergens↗

PubMed1996

Plant profilins rescue the aberrant phenotype of profilin-deficient Dictyostelium cells.

To characterize the function of plant profilins in vivo, we expressed two pollen specific Zea mays (maize) profilin isoforms in profilin-minus Dictyostelium discoideum mutants. In maize, profilins exist as a multigene family containing 4 or more members which are highly similar to each other but substantially less similar to profilins from animals and lower eukaryotes. Previously we have shown that D. discoideum profilin-minus cells have an aberrant phenotype due to defects in cell shape, cytokinesis, and development. These defects could be rescued by introducing the pollen-specific profilins 1 or 2 from maize using a newly constructed expression vector. Expression of the heterologous profilins in Dictyostelium clones was assayed by affinity purification of the pollen profilins with poly-proline agarose and by immunoblotting with a polyclonal antiserum raised against maize pollen profilin. In contrast to the profilin-minus mutants, Dictyostelium cells expressing plant profilins showed normal cell shape, contained less F-actin, and were able to form fruiting bodies. These data provide genetic evidence that maize pollen profilins, even though they are specific for a distinct developmental stage, share functional properties with profilin from a lower eukaryote and apparently act as G-actin-sequestering proteins in this system.

Animals↗

PubMed2003

Depolymerization of actin filaments by profilin. Effects of profilin on capping protein function.

Profilin interacts with the barbed ends of actin filaments and is thought to facilitate in vivo actin polymerization. This conclusion is based primarily on in vitro kinetic experiments using relatively low concentrations of profilin (1-5 microm). However, the cell contains actin regulatory proteins with multiple profilin binding sites that potentially can attract millimolar concentrations of profilin to areas requiring rapid actin filament turnover. We have studied the effects of higher concentrations of profilin (10-100 microm) on actin monomer kinetics at the barbed end. Prior work indicated that profilin might augment actin filament depolymerization in this range of profilin concentration. At barbed-end saturating concentrations (final concentration, approximately 40 microm), profilin accelerated the off-rate of actin monomers by a factor of four to six. Comparable concentrations of latrunculin had no detectable effect on the depolymerization rate, indicating that profilin-mediated acceleration was independent of monomer sequestration. Furthermore, we have found that high concentrations of profilin can successfully compete with CapG for the barbed end and uncap actin filaments, and a simple equilibrium model of competitive binding could explain these effects. In contrast, neither gelsolin nor CapZ could be dissociated from actin filaments under the same conditions. These differences in the ability of profilin to dissociate capping proteins may explain earlier in vivo data showing selective depolymerization of actin filaments after microinjection of profilin. The finding that profilin can uncap actin filaments was not previously appreciated, and this newly discovered function may have important implications for filament elongation as well as depolymerization.

Actins↗

PubMed2000

Alternative splicing of the mouse profilin II gene generates functionally different profilin isoforms.

Profilins are a conserved family of proteins participating in actin dynamics and cell motility. In the mouse, two profilin genes are known. Profilin I is expressed universally at high levels, while profilin II is expressed mainly in the brain. Here we describe the occurrence of two mouse profilin II isoforms, A and B, which are derived by alternative splicing. They are identical through residue 107 of the protein, but then have distinct C-terminal sequences. Profilin IIA binds to poly-L-proline and actin with high affinity similar to profilin I. Profilin IIB on the other hand does not bind to actin and the affinity for poly-L-proline is greatly diminished. However, tubulin was found to bind to GST-profilin IIB, and in vivo GFP-profilin IIB was recruited to spindles and asters during mitosis in HeLa cells. Our results indicate unexpected diversity in the functions of the profilin family of proteins, and suggest that in mouse profilin IIA is intimately involved in actin dynamics, while profilin IIB associates with other cytoskeletal components.

Alternative Splicing↗

PubMed1999

X-ray structure determination of human profilin II: A comparative structural analysis of human profilins.

Human profilins are multifunctional, single-domain proteins which directly link the actin microfilament system to a variety of signalling pathways via two spatially distinct binding sites. Profilin binds to monomeric actin in a 1:1 complex, catalyzes the exchange of the actin-bound nucleotide and regulates actin filament barbed end assembly. Like SH3 domains, profilin has a surface-exposed aromatic patch which binds to proline-rich peptides. Various multidomain proteins including members of the Ena/VASP and formin families localize profilin:actin complexes through profilin:poly-L-proline interactions to particular cytoskeletal locations (e.g. focal adhesions, cleavage furrows). Humans express a basic (I) and an acidic (II) isoform of profilin which exhibit different affinities for peptides and proteins rich in proline residues. Here, we report the crystallization and X-ray structure determination of human profilin II to 2.2 A. This structure reveals an aromatic extension of the previously defined poly-L-proline binding site for profilin I. In contrast to serine 29 of profilin I, tyrosine 29 in profilin II is capable of forming an additional stacking interaction and a hydrogen bond with poly-L-proline which may account for the increased affinity of the second isoform for proline-rich peptides. Differential isoform specificity for proline-rich proteins may be attributed to the differences in charged and hydrophobic residues in and proximal to the poly-L-proline binding site. The actin-binding face remains nearly identical with the exception of five amino acid differences. These observations are important for the understanding of the functional and structural differences between these two classes of profilin isoforms.

Acids↗

PubMed1989

Acanthamoeba actin and profilin can be cross-linked between glutamic acid 364 of actin and lysine 115 of profilin.

Acanthamoeba profilin was cross-linked to actin via a zero-length isopeptide bond using carbodiimide. The covalently linked 1:1 complex was purified and treated with cyanogen bromide. This cleaves actin into small cyanogen bromide (CNBr) peptides and leaves the profilin intact owing to its lack of methionine. Profilin with one covalently attached actin CNBr peptide was purified by gel filtration followed by gel electrophoresis and electroblotting on polybase-coated glass-fiber membranes. Since the NH2 terminus of profilin is blocked, Edman degradation gave only the sequence of the conjugated actin CNBr fragment beginning with Trp-356. The profilin-actin CNBr peptide conjugate was digested further with trypsin and the cross-linked peptide identified by comparison with the tryptic peptide pattern obtained from carbodiimide-treated profilin. Amino-acid sequence analysis of the cross-linked tryptic peptides produced two residues at each cycle. Their order corresponds to actin starting at Trp-356 and profilin starting at Ala-94. From the absence of the phenylthiohydantoin-amino acid residues in specific cycles, we conclude that actin Glu-364 is linked to Lys-115 in profilin. Experiments with the isoforms of profilin I and profilin II gave identical results. The cross-linked region in profilin is homologous with sequences in the larger actin filament capping proteins fragmin and gelsolin.

Acanthamoeba↗

PubMed1998

In mouse brain profilin I and profilin II associate with regulators of the endocytic pathway and actin assembly.

Profilins are thought to be essential for regulation of actin assembly. However, the functions of profilins in mammalian tissues are not well understood. In mice profilin I is expressed ubiquitously while profilin II is expressed at high levels only in brain. In extracts from mouse brain, profilin I and profilin II can form complexes with regulators of endocytosis, synaptic vesicle recycling and actin assembly. Using mass spectrometry and database searching we characterized a number of ligands for profilin I and profilin II from mouse brain extracts including dynamin I, clathrin, synapsin, Rho-associated coiled-coil kinase, the Rac-associated protein NAP1 and a member of the NSF/sec18 family. In vivo, profilins co-localize with dynamin I and synapsin in axonal and dendritic processes. Our findings strongly suggest that in brain profilin I and profilin II complexes link the actin cytoskeleton and endocytic membrane flow, directing actin and clathrin assembly to distinct membrane domains.

Actins↗

PubMed1996

The Arabidopsis profilin gene family. Evidence for an ancient split between constitutive and pollen-specific profilin genes.

Profilin is a ubiquitous eukaryotic protein that regulates the actin cytoskeleton and recently has been identified as a potent allergen in pollen. We examined the profilin gene family in the model plant, Arabidopsis thaliana, and found that it contained approximately 8 to 10 members. Four distinct profilin sequences, three cDNAs, PRF1, PRF2, and PRF3, and two genomic clones, PRF1 and PRF4, were isolated and characterized. These genes encoded four distinct profilin isoforms of 131 to 134 amino acids. Northern and reverse-transcriptase polymerase chain reaction analyses demonstrated that Arabidopsis PRF1 was expressed in all major plant organs, whereas PRF4 was specifically expressed in mature pollen. Gene trees constructed from amino acid sequence data revealed the presence of two ancient, distinct profilin gene classes in plants. PRF4 was in a class with previously identified pollen-specific profilins from monocot and dicot species. PRF1, PRF2, PRF3, and a distant dicot sequence formed a separate novel class, suggesting an ancient separation of plant profilins based on regulation and perhaps function. The coevolution of plant actin and profilin classes with similar patterns of expression is discussed. The similarity of plant, fungal, protist, insect, and nematode profilins and their extreme divergence from the vertebrate profilins has striking implications for the evolution of fungal-spore- and plant-pollen-profilins as allergens.

Allergens↗

PubMed2000

[Incidence of sensitization to profilin in a population allergic to pollen: responsibility of profilin in pollen polysensitizations in patients with a normal level of total IgE].

UNLABELLED: The study had the aim of establishing the incidence of sensitization to profilin (a panallergen found in pollens and foods of vegetal origin) in pollen-allergic patients. We evaluated the consequences of such sensitizations on the results of specific IgE, the positivity of skin tests and clinical signs. METHODS: 94 consenting patients, allergic to pollens (trees and/or grasses and/or weeds) replied to a questionnaire and had skin tests to purified profilin and measurement of serum anti-profilin IgE. RESULTS: Two groups were defined: one group was sensitized to profilin (GSP), with positive skin test and anti profilin IgE of 31 patients, and a group non-sensitive to profilin (GNSP) (negative skin test and anti-profilin IgE) of 41 patients. Discordant results were found in 22 patients. Taking in account the two groups, sensitization to profilin was 43%. The two groups were homogenous for age, sex, ethnics and clinical signs. Food allergy was more frequent but not statistically different (p = 0.09) in the group GSP (51.6%) than the GNSP (31.7%), in particular allergy to fruits of the Rosaceae family. Pollen polysensitization (to three species, trees, weeds and grasses) was more frequent in the GSP group (64.5%) than the GNSP (12.5). Polysensitization to pollens and foods was also more frequent in the sensitized group (65.5%) than in the non-sensitized group (12.5%). In a sub-group with normal levels of total IgE pollen polysensitization was more frequent in patients who were sensitive to profilin. On biological investigation, sensitization to profilin influenced the result of anti-latex IgE and also the IgE to many vegetal allergens. These results show the value of seeking a sensitization to profilin in patients with pollinoses.

Adult↗

PubMed2004

Parietaria profilin shows only limited cross-reactivity with birch and grass profilins.

BACKGROUND: In patients showing multiple reactivity to seasonal airborne allergens, a skin prick test (SPT) with Parietaria pollen scores frequently negative, suggesting that profilin from Parietaria might not share IgE-binding epitopes with profilin from botanically unrelated airborne allergens. This study investigated the immunologic cross-reactivity between profilins from Parietaria, grass and birch pollen. METHODS: 36 patients hypersensitive to birch profilin, Bet v 2, underwent SPT with Parietaria, and IgE to both whole Parietaria pollen and Phleum profilin were sought in their sera by ELISA. In ELISA inhibition studies, IgE reactivity to Phleum profilin was measured before and after absorption of sera from Parietaria reactors with both whole Parietaria pollen extract, and Par j 1/Par j 2 fraction. Further, their IgE reactivity to whole Parietaria pollen was measured before and after absorption with the Par j 1/Par j 2 fraction. RESULTS: All sera showed IgE reactivity to Phleum profilin. Only 14/36 (39%) patients had a positive SPT to Parietaria and 17/36 (47%) showed IgE to Parietaria. Absorption of sera from Parietaria reactors with whole Parietaria extract caused a marked reduction in IgE reactivity to grass profilin; in contrast, absorption of sera with the Par j 1/Par j 2 fraction did not exert any inhibitory effect on IgE reactivity to grass profilin. Absorption of sera with the Par j 1/Par j 2 fraction markedly reduced IgE reactivity to whole Parietaria extract in 8/9 cases. CONCLUSION: Less than 50% of patients sensitized to birch and grass profilin cross-react to Parietaria profilin. In most cases, cross-reactors are hypersensitive to major, specific Parietaria allergens as well. This findings may be of practical relevance when the prescription of specific immunotherapy is considered.

Adolescent↗

PubMed2000

Profilin II is alternatively spliced, resulting in profilin isoforms that are differentially expressed and have distinct biochemical properties.

We deduced the structure of the mouse profilin II gene. It contains five exons that can generate four different transcripts by alternative splicing. Two transcripts encode different profilin II isoforms (designated IIa and IIb) that have similar affinities for actin but different affinities for polyphosphoinositides and proline-rich sequences. Profilins IIa and IIb are also present in humans, suggesting that all mammals have three profilin isoforms. Profilin I is the major form in all tissues, except in the brain, where profilin IIa is most abundant. Profilin IIb appears to be a minor form, and its expression is restricted to a limited number of tissues, indicating that the alternative splicing is tightly regulated. Western blotting and whole-mount in situ hybridization show that, in contrast to the expression of profilin I, the expression level of profilin IIa is developmentally regulated. In situ hybridization of adult brain sections reveals overlapping expression patterns of profilins I and IIa.

Alternative Splicing↗

PubMed1998

Localization of actobindin, profilin I, profilin II, and phosphatidylinositol-4,5-bisphosphate (PIP2) in Acanthamoeba castellanii.

Specific polyclonal antisera were raised against purified Acanthamoeba actobindin and synthetic peptides corresponding to regions of maximum charge differences in Acanthamoeba profilin I and profilin II. Immunofluorescence studies with these antibodies showed profilin I to be distributed throughout the Acanthamoeba cytoplasm, except for lamellipodia, with the highest fluorescence intensity in cortical regions in which monomeric actin also was present, as shown by labeling with fluorescent DNase. In contrast, profilin II appeared to be uniformly associated with the plasma membrane except at sites of pseudopod extension, where the concentration was frequently decreased, in addition to cortical regions. Immunofluorescence studies using a monoclonal antibody specific for phosphatidylinositol-4,5-bisphosphate (PIP2) suggested that its distribution is mostly limited to the plasma membrane. In contrast to the distribution of profilin II, PIP2 immunofluorescence was prominent at the leading edge of cells, including the plasma membrane of lamellipodia. Quantitative immunoelectron microscopy showed that profilin II was approximately 36 times more likely to localize to the plasma membrane than profilin I. Immunofluorescence and confocal microscopy localized actobindin to the base of lamellipodia. The differential localization of the three actin monomer-binding proteins suggests that they have different biologic functions in Acanthamoeba and is consistent with the hypotheses that (1) profilin I functions predominantly as an actin monomer-binding protein; (2) profilin II regulates, or is regulated by, PIP2; and (3) actobindin inhibits nucleation of new filaments and facilitates elongation of existing polarized filaments in actively motile regions.

Acanthamoeba↗

PubMed1995

Molecular cloning and characterization of profilin from tobacco (Nicotiana tabacum): increased profilin expression during pollen maturation.

Profilin has recently been identified as an actin-binding protein in higher plants. A cDNA coding for tobacco profilin, which shared an average sequence identity of 75% with other plant profilins, was isolated from a tobacco pollen cDNA library by antibody screening. Tobacco profilin was expressed in Escherichia coli and purified by affinity to poly-(L-proline) Sepharose. A rabbit antiserum was raised against recombinant tobacco profilin and used to estimate the amount of profilin expressed in different tobacco tissues. Profilin can be detected in different somatic tissues, but the expression is 50-100 fold higher in mature pollen. Immunofluorescence and confocal laser scanning microscopy showed a homogeneous distribution of profilin in the cytoplasm of in vitro cultured pollen grains and pollen tubes of tobacco whereas some growing pollen tubes were stained more intensively a their tip. A possible role of pollen profilin as a developmentally upregulated microfilament precursor in mature pollen is discussed.

Actins↗