Biomedical subjects

T Pan

Publications and source records attributed to T Pan.

At least 55 records · Page 3Linked to original sources

PubMed2000

Crk1, a novel Cdc2-related protein kinase, is required for hyphal development and virulence in Candida albicans.

Both mitogen-activated protein kinases and cyclin-dependent kinases play a role in hyphal development in Candida albicans. Using an oligonucleotide probe-based screen, we have isolated a new member of the Cdc2 kinase subfamily, designated Crk1 (Cdc2-related kinase). The protein sequence of Crk1 is most similar to those of Saccharomyces cerevisiae Sgv1 and human Pkl1/Cdk9. In S. cerevisiae, CRK1 suppresses some, but not all, of the defects associated with an sgv1 mutant. Deleting both copies of CRK1 in C. albicans slows growth slightly but leads to a profound defect in hyphal development under all conditions examined. crk1/crk1 mutants are impaired in the induction of hypha-specific genes and are avirulent in mice. Consistent with this, ectopic expression of the Crk1 kinase domain (CRK1N) promotes filamentous or invasive growth in S. cerevisiae and hyphal development in C. albicans. The activity of Crk1 in S. cerevisiae requires Flo8 but is independent of Ste12 and Phd1. Similarly, Crk1 promotes filamentation through a route independent of Cph1 and Efg1 in C. albicans. RAS1(V13) can also activate filamentation in a cph1/cph1 efg1/efg1 double mutant. Interestingly, CRK1N produces florid hyphae in ras1/ras1 strains, while RAS1(V13) generates feeble hyphae in crk1/crk1 strains.

Amino Acid Sequence↗

PubMed2000

KGF regulates pulmonary epithelial proliferation and surfactant protein gene expression in adult rat lung.

Keratinocyte growth factor (KGF, FGF-7) is a potent mitogen for epithelial cells. We instilled recombinant human KGF to determine the effects of KGF on alveolar epithelial cells. Left lungs of adult rats were instilled intrabronchially with KGF (5 mg/kg) or normal saline. KGF instillation resulted in epithelial cell hyperplasia, and the alveolar bromodeoxyuridine (BrdU) labeling index peaked at 35% on day 2 after instillation. The mRNA levels for the surfactant proteins (SPs) SP-A, SP-B, and SP-D were increased in whole lung tissue on days 1 and 2 after KGF treatment and then returned to control levels on days 3-7. SP-C mRNA levels were increased on days 2-5 after KGF instillation. However, all surfactant protein mRNAs were reduced in type II cells isolated from rats instilled with KGF 2 or 3 days before isolation. These observations were confirmed by in situ hybridization. Instillation of KGF also increased the amount of SP-A and SP-D in lavage fluid. Transcripts for CC10, the 10-kDa Clara cell protein, were decreased. KGF increases the mRNA for the surfactant proteins per lung because of type II cell hyperplasia, but the mRNA per cell is slightly diminished as measured in isolated cells or estimated by in situ hybridization.

Age Factors↗

PubMed2000

Effect of adenovector-mediated gene transfer of keratinocyte growth factor on the proliferation of alveolar type II cells in vitro and in vivo.

Alveolar type II cell proliferation occurs after lung injury and is thought to minimize the subsequent fibrotic response. Keratinocyte growth factor (KGF) has been shown to be a potent growth factor for rat alveolar type II cells. In this study, we created a replication-deficient, recombinant human type 5 adenovirus vector expressing human KGF (Ad5-KGF) to produce alveolar type II cell hyperplasia in vivo. In rat type II cells in vitro, Ad5-KGF at a multiplicity of infection (MOI) of 2, 4, and 8 plaque-forming units (PFU)/cell increased thymidine incorporation 13.3-, 16.8-, and 20. 8-fold, respectively. The KGF concentration in the medium increased up to 26.0 +/- 1.0 ng/ ml. We then instilled 10(9) PFU of Ad5-KGF, Ad5-LacZ, or phosphate-buffered saline into Fischer 344 rats and analyzed the lungs 2, 3, 7, 14, 21, and 28 d later. Ad5-KGF produced extensive alveolar type II cell hyperplasia on Days 2, 3, and 7. Surfactant protein (SP)-A and SP-D in lavage and SP-D in serum increased more in the Ad5-KGF group than in the Ad5-LacZ and PBS groups on Days 2 and 3. KGF was readily detectable for up to 7 d in lavage fluid, although only a modest number of cells expressed KGF messenger RNA as detected by in situ hybridization. These data show that Ad5-KGF stimulates extensive alveolar type II cell proliferation in vivo.

Adenoviridae↗

PubMed1999

Applicability of urea in the thermodynamic analysis of secondary and tertiary RNA folding.

The equilibrium folding of a series of self-complementary RNA duplexes and the unmodified yeast tRNA(Phe) is studied as a function of urea and Mg(2+) concentration with optical spectroscopies and chemical modification under isothermal conditions. Via application of standard methodologies from protein folding, the folding free energy and its dependence on urea concentration, the m value, are determined. The free energies of the RNA duplexes obtained from the urea titrations are in good agreement with those calculated from thermal melting studies [Freier, S. I., et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 9373]. The m value correlates with the length of the RNA duplex and is not sensitive to ionic conditions and temperature. The folding of the unmodified yeast tRNA(Phe) can be described by two Mg(2+)-dependent transitions, the second of which corresponds to the formation of the native tertiary structure as confirmed by hydroxyl radical protection and partial nuclease digestion. Both transitions are sensitive to urea and have m values of 0.94 and 1.70 kcal mol(-)(1) M(-)(1), respectively. Although the precise chemical basis of urea denaturation of RNA is uncertain, the m values for the duplexes and tRNA(Phe) are proportional to the amount of the surface area buried in the folding transition. This proportionality, 0.099 cal mol(-)(1) M(-)(1) A(-)(2), is very similar to that observed for proteins, 0.11 cal mol(-)(1) M(-)(1) A(-)(2) [Myers, J., Pace, N., and Scholtz, M. (1995) Protein Sci. 4, 2138]. These results indicate that urea titration can be used to measure both the free energy and the magnitude of an RNA folding transition.

Base Sequence↗

PubMed1999

A thermodynamic framework and cooperativity in the tertiary folding of a Mg2+-dependent ribozyme.

The folding thermodynamics of the catalytic domain from the Bacillus subtilis RNase P RNA is analyzed using circular dichroism and fluorescence spectroscopies, hydroxyl radical protection, and catalytic activity. Folding of this 255-nucleotide ribozyme can be described with three populated species: unfolded (U), intermediate (I), and native (N) states. The U-to-I transition primarily involves secondary structure formation, whereas the I-to-N transition is dominated by tertiary structure formation. The I-to-N transition is highly cooperative as indicated by the coincidence of the four probes applied here. Two isothermal methods are used to determine the stability of the N state relative to the I state at 10 and 37 degrees C. The first method measures the extent of Mg(2+)-induced folding without urea or at constant urea concentrations. The second method measures the extent of urea-induced unfolding at constant Mg(2+) concentrations. Via application of a cooperative binding analysis, the Mg(2+) transition midpoint (K(Mg)), the Hill constant (n), and the urea-dependent surface burial parameter (m value) determined by both methods are identical, indicating that they report the same, reversible folding event. Three conclusions can be drawn from these results. (i) The folding free energy of a Mg(2+)-dependent tertiary RNA structure can be described by the K(Mg) and n parameters according to a cooperative Mg(2+) binding model. (ii) The Hill constant for this tertiary RNA structure probably represents the differential number of Mg(2+) ions bound in the I-to-N transition. (iii) Under physiological conditions, the stability of this large ribozyme is similar to that of small globular proteins.

Bacillus subtilis↗

PubMed1999

Design and isolation of ribozyme-substrate pairs using RNase P-based ribozymes containing altered substrate binding sites.

Substrate recognition and cleavage by the bacterial RNase P RNA requires two domains, a specificity domain, or S-domain, and a catalytic domain, or C-domain. The S-domain binds the T stem-loop region in a pre-tRNA substrate to confer specificity for tRNA substrates. In this work, the entire S-domain of the Bacillus subtilis RNase P RNA is replaced with an artificial substrate binding module. New RNA substrates are isolated by in vitro selection using two libraries containing random regions of 60 nt. At the end of the selection, the cleavage rates of the substrate library are approximately 0.7 min(-1)in 10 mM MgCl(2)at 37 degrees C, approximately 4-fold better than the cleavage of a pre-tRNA substrate by the wild-type RNase P RNA under the same conditions. The contribution of the S-domain replacement to the catalytic efficiency is from 6- to 22 000-fold. Chemical and nuclease mapping of two ribozyme-product complexes shows that this contribution correlates with direct interactions between the S-domain replacement and the selected substrate. These results demonstrate the feasibility of design and isolation of RNase P-based, matching ribozyme-substrate pairs without prior knowledge of the sequence or structure of the interactive modules in the ribozyme or substrate.

Bacillus subtilis↗

PubMed1999

Folding of a large ribozyme during transcription and the effect of the elongation factor NusA.

We compared in vitro transcription-initiated folding of the ribozyme from Bacillus subtilis RNase P to refolding from the full-length, denatured state by monitoring the appearance of its catalytic activity. At 37 degrees C, Mg(2+)-initiated refolding of the wild type and a circularly permutate ribozyme takes minutes and is limited by a kinetic trap. Transcription by T7 RNA polymerase alters the folding pathway of both RNAs and introduces new kinetic traps. Transcription by the core Escherichia coli RNA polymerase yields the same result, in spite of its 4-fold-slower elongation rate. However, the presence of its elongation factor NusA accelerates more than 10-fold the transcription-initiated folding of the circularly, permutated ribozyme by E. coli RNA polymerase. The effect of NusA likely is caused by its enhancement of transcriptional pausing because NusA did not accelerate transcription-initiated folding using a mutant RNA polymerase that failed to pause or respond to NusA during ribozyme synthesis. We conclude that both transcription and specific pausing therein can alter RNA-folding pathways.

Bacillus subtilis↗

PubMed1999

The cleavage step of ribonuclease P catalysis is determined by ribozyme-substrate interactions both distal and proximal to the cleavage site.

The cleavage step of bacterial RNase P catalysis involves concentration-independent processes after the formation of the ribozyme-substrate complex that result in the breaking of a phosphodiester bond. The 2'OH group at the cleavage site of a pre-tRNA substrate is an important determinant in the cleavage step. We determined here that in contrast to a tRNA substrate, the 2'OH at the cleavage site of two in vitro selected substrates has no effect, whereas a 2'OH located adjacent to the cleavage site has a similarly large effect on the cleavage step. This result indicates that a unique 2'OH in the vicinity of the cleavage site interacts with the ribozyme to achieve the maximal efficiency of the cleavage step. Individual modifications in a pre-tRNA substrate that disrupt ES interactions proximal to the cleavage site generally have little effect on the usage of this unique 2'OH. Ribozyme modifications that delete the interactions involving the T stem-loop of the tRNA have a large effect on the usage of this unique 2'OH and also alter the location of this 2'OH. We propose a new ES complex prior to the bond-breaking step in the reaction scheme to explain these results. This second ES complex is in fast equilibrium with the initial ES complex formed by bimolecular collision. The ribozyme interaction with this unique 2'OH shifts the equilibrium in favor of the second ES complex. The formation of the second ES complex may require optimal geometry of the two independently folding domains of this ribozyme to precisely position crucial functional groups and Mg2+ ions in the active site. Such a domain geometry is significantly favored by the RNase P protein. In the absence of the protein, spatial rearrangement of these domains in the ES complex may be necessary.

Bacillus subtilis↗

PubMed1999

Pathway modulation, circular permutation and rapid RNA folding under kinetic control.

The thermodynamics and folding kinetics of a circularly permuted construct of the ribozyme from Bacillus subtilis RNase P are analyzed and compared with the folding properties of the wild-type ribozyme using optical spectroscopy and catalytic activity. The folding of the wild-type ribozyme is slow due to the rearrangement of kinetically trapped species containing misfolded structures. To test whether any misfolded structure arises from interactions between the two independently folding domains of the RNase P RNA, a circular permuted form was created where one of the two phosphodiester bonds connecting these domains is broken. This construct folds approximately 15-fold faster (t1/2 approximately nine seconds) than the wild-type ribozyme at 37 degreesC. While the complete folding of both domains is kinetically indistinguishable in the wild-type ribozyme, one domain folds much faster than the other domain in the circularly permuted construct. Hence, the major kinetic trap in the folding of the wild-type RNase P RNA involves interdomain interactions. This kinetic trap is avoidable at 37 degreesC in the circularly permuted RNA. However, at temperatures below 30 degreesC or when refolding begins from an equilibrium intermediate stabilized by submillimolar concentrations of Mg2+, a subpopulation containing an interdomain misfold still forms. These results indicate that the folding pathway of this large RNA is highly malleable and can be under kinetic control.

Bacillus subtilis↗

PubMed1999

Transferrin is an essential factor for myelination.

It has been established that oligodendrocytes, the myelin forming cells, participate in iron homeostasis through the synthesis and secretion of transferrin. Here we investigated whether a correlation exists between myelination, the commonly studied function of oligodendrocytes, and that of transferrin synthesis and secretion. We used a proteolipid protein mutant, the myelin deficient rat, whose condition is characterized by severe hypomyelination. We compared the ontogenic profile for transferrin gene expression in mutants with that of unaffected rat pups through northern blot analysis and in situ hybridization. Surprisingly, transferrin synthesis was null in mutant oligodendrocytes. Next, we demonstrated that a single apo-transferrin intraparenchymal injection administered to P5 rat pups enabled mutant oligodendrocytes to synthesize myelin basic protein and to myelinate axons, indicating that transferrin effects mutant oligodendrocyte maturation regardless of its source. Thus, transferrin availability is essential for oligodendrocyte maturation and function, and oligodendrocytes are most vulnerable to transferrin deficiency during the premyelinating stage.

Animals↗

PubMed1999

Inhibition of 6-methyladenine formation decreases the translation efficiency of dihydrofolate reductase transcripts.

Cycloleucine was used to inhibit the formation of internal N6-methyladenosine residues in the messenger ribonucleic acid transcripts from cultured methotrexate resistant mouse sarcoma cells. Cells cultured in cycloleucine produced transcripts deficient in N6-methyladenosine residues and the 2'-O-methylated nucleosides of the cap structure; however, the formation of the 7-methylguanine nucleoside of the cap was not effected. Cytoplasmic polyadenylated transcripts were isolated from cells which had been pretreated with media containing cycloleucine and translated in an in vitro translation assay. The levels of translated dihydrofolate reductase were then analyzed by polyacrylamide gel electrophoresis. The amount of dihydrofolate reductase protein produced from the transcripts of the cycloleucine treated cells was 20% less than untreated transcripts. Ribonuclease protection assays demonstrated little difference in the cytoplasmic levels of dihydrofolate reductase transcripts between treated and untreated cells suggesting that the decrease in translation efficiency was not caused solely by an alteration in the processing or cytoplasmic transport of the transcripts. Translation of in vitro transcribed transcripts showed the presence of 2'-O-methylated nucleosides in the cap structure had a negative effect on translation efficiency, demonstrating that the results observed from cycloleucine treatment could not be due to the inhibition of 2'-O-methylation in the cap. These experiments therefore suggest that an inhibition of N6-methyladenosine residues in dihydrofolate reductase transcripts significantly alters their rate of translation.

Adenine↗

PubMed1999

Keratinocyte growth factor-induced hyperplasia of rat alveolar type II cells in vivo is resolved by differentiation into type I cells and by apoptosis.

Keratinocyte growth factor (KGF) is a potent mitogen of alveolar epithelial type II cells (AEII). AEII hyperplasia is resolved within several days following intratracheal instillation of KGF by unknown mechanism(s). AEII hyperplasia was induced in rat lungs by intrabronchial instillation of 5 mg recombinant human (rh)KGF x kg body weight(-1) or an equivalent amount of diluent. Epithelial architecture, cell proliferation, transformation of AEII into type I cells (AEI) and apoptosis were investigated by means of immunohistochemistry, stereology, double immunofluorescence microscopy, electron microscopy and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) technique in lungs fixed 1, 2, 3 and 7 days after treatment. After 1 day of rhKGF instillation, an increase was observed in the nuclear antigen Ki-67, a proliferation marker detected by the antibody MIB-5-expressing surfactant protein (SP)-B, -C, -D-positive AEII. The incidence of mitosis was increased by day 2, resulting in AEII micropapillae with intense basolateral expression of the exon 6 containing isoform (v6) of CD446 (CD44v6), a marker for AEII. By day 3, monolayers of AEII exhibiting lateral CD44v6 covered 45% of the alveolar surface. After 7 days, there were numerous intermediate AEII/AEI cells characterized by a flat elongated shape, staining for SP-D, apical appearance of AEI marker Lycopersicon esculentum lectin and lateral staining for AEII marker CD44v6. Increased numbers of TUNEL-positive epithelial cells were seen at days 2-7. In conclusion, restoration of normal alveolar epithelium after instillation of recombinant human keratinocyte growth factor is accomplished by terminal differentiation and apoptosis of hyperplastic alveolar epithelial type II cells in vivo.

Animals↗

PubMed1999

Mg2+-dependent folding of a large ribozyme without kinetic traps.

The folding kinetics of the catalytic domain of Bacillus subtilis ribonuclease P is analyzed here by fluorescence and catalytic activity. The folding pathway is apparently free of kinetic traps, as indicated by a decrease in folding rates upon the addition of urea. We apply Mg2+ and urea chevron analysis to fully describe the folding and unfolding kinetics of this ribozyme. A folding scheme containing two kinetic intermediates completely accounts for the free energy, the Mg2+ Hill coefficient and the surface buried in the equilibrium transition. At saturating Mg 2+concentrations, folding is limited by a barrier that is independent of Mg2+ and urea. These results describe the first trap-free folding pathway of a large ribozyme and indicate that kinetic traps are not an obligate feature of RNA folding.

Animals↗

PubMed1999

Saccharomyces cerevisiae G1 cyclins are differentially involved in invasive and pseudohyphal growth independent of the filamentation mitogen-activated protein kinase pathway.

Several lines of evidence suggest that the morphogenetic transition from the yeast form to pseudohyphae in Saccharomyces cerevisiae may be regulated by the cyclin-dependent kinase (Cdk). To examine this hypothesis, we mutated all of the G1 cyclin genes in strains competent to form pseudohyphae. Interestingly, mutation of each G1 cyclin results in a different filamentation phenotype, varying from a significant defect in cln1/cln1 strains to enhancement of filament production in cln3/cln3 strains. cln1 cln2 double mutants are more defective in pseudohyphal development and haploid invasive growth than cln1 strains. FLO11 transcription, which correlates with the level of invasive growth, is low in cln1 cln2 mutants and high in grr1 cells (defective in proteolysis of Cln1,2), suggesting that Cln1,2/Cdks regulate the pseudohyphal transcriptional program. Epistasis analysis reveals that Cln1,2/Cdk and the filamentation MAP kinase pathway function in parallel in regulating filamentous and invasive growth. Cln1 and Cln2, but not Ste20 or Ste12, are responsible for most of the elevated FLO11 transcription in grr1 strains. Furthermore, phenotypic comparison of various filamentation mutants illustrates that cell elongation and invasion/cell-cell adhesion during filamentation are separable processes controlled by the pseudohyphal transcriptional program. Potential targets for G1 cyclin/Cdks during filamentous growth are discussed.

Cell Division↗

PubMed1998

Recognition of a pre-tRNA substrate by the Bacillus subtilis RNase P holoenzyme.

The holoenzyme of the bacterial RNase P has broader selectivity for biological substrates compared to the RNA alone (denoted P RNA) reaction. The structural basis of the substrate selectivity is investigated using a pre-tRNA substrate containing single-atom modifications by single turnover kinetics. Hydroxyl radical protection of the holoenzyme in the absence of the substrate shows that the RNase P protein binds to several regions in P RNA. The holoenzyme interacts with a subset of functional groups in the T stem-loop region of a pre-tRNA substrate previously identified to directly contact P RNA. The subtle change in structural recognition allows the holoenzyme to recognize RNA structures with only a small perturbation in an A-form helix at the corresponding position of the T stem-loop. This altered profile may permit the holoenzyme to bind non-tRNA substrates with little change in catalytic efficiency. The holoenzyme recognizes the same set of functional groups as the P RNA reaction in the region around the cleavage site and shows similar cleavage site selection compared to the P RNA reaction. These results suggest that the holoenzyme does not alter the fundamental mechanism of this enzymatic reaction. Rather, the holoenzyme significantly affects the binding affinity of an RNA substrate through additional interactions with the 5' leader [Kurz, C. A., Niranjanakumari, S., and Fierke, C. A. (1998) Biochemistry 37, 2393] and through altered recognition of the substrate structure.

Bacillus subtilis↗

PubMed1998

Interaction of structural modules in substrate binding by the ribozyme from Bacillus subtilis RNase P.

The ribozyme from bacterial ribonuclease P recognizes two structural modules in a tRNA substrate: the T stem-loop and the acceptor stem. These two modules are connected through a helical linker. The T stem-loop binds at a surface confined in a folding domain away from the active site. Substrates for the Bacillus subtilis RNase P RNA were previously selected in vitro that are shown to bind comparably well or better than a tRNA substrate. Chemical modification of P RNA-substrate complexes with dimethylsulfate and kethoxal was performed to determine how the P RNA recognizes three in vitro selected substrates. All three substrates bind at the surface known to interact with the T stem-loop of tRNA. Similar to a tRNA, the secondary structure of these substrates contains a helix around the cleavage site and a hairpin loop at the corresponding position of the T stem-loop. Unlike a tRNA, these two structural modules are connected through a non-helical linker. The two structural modules in the tRNA and in the selected substrates bind to two different domains in P RNA. The properties of substrate recognition exhibited by this ribozyme may be exploited to isolate new ribozyme-substrate pairs with interactive structural modules.

Bacillus subtilis↗

PubMed1998

Recognition of the 5' leader and the acceptor stem of a pre-tRNA substrate by the ribozyme from Bacillus subtilis RNase P.

The catalysis by the ribozyme from bacterial RNase P involves specific interactions with the structure of the tRNA substrate. Recognition of the T stem-loop by this ribozyme occurs in a groove-like structure dictated by the tertiary folding of tRNA [Loria, A., and Pan, T. (1997) Biochemistry 36, 6317]. Effects of 2'-OH --> 2'-H modifications within the acceptor stem and the 5' leader on substrate binding and catalysis are determined using a tRNAPhe substrate that is significantly cleaved at more than one site. In all but one case, the 2'-deoxy substitution has little effect on binding for cleavage at the correct and incorrect sites. Substitution of the 2'-OH group at the correct site, however, decreases the cleavage chemistry by more than 3.4 kcal/mol for cleavage at both the correct and incorrect sites. Substitutions of the 2'-OH groups at the incorrect sites have no effect for cleavage at the incorrect and correct sites. Truncation of the 5' leader results in differential effects on cleavage at different sites. These observations lead to a model in which cleavage at the correct and incorrect sites involves formation of different ribozyme-substrate complexes depending on binding of specific nucleotides in the 5' leader. Binding of the T stem-loop of tRNA and the 2'-OH group at the correct cleavage site is common for all ES complexes. An A/U-rich 5' leader significantly promotes formation of the ES complex and accelerates the cleavage chemistry over those of a C/G-rich 5' leader, but only moderately enhances cleavage at the correct site over cleavage at the incorrect sites. Since cleavage at different sites requires formation of different ES complexes, cleavage site selection can occur at the level of the ES complex and at the chemical step.

Bacillus subtilis↗

PubMed1998

A toxin homology domain in an astacin-like metalloproteinase of the jellyfish Podocoryne carnea with a dual role in digestion and development.

Metalloproteinases of the astacin family such as tolloid play major roles in animal morphogenesis. Cnidarians are thought to be evolutionary simple organisms and, therefore, a metalloproteinase from the marine hydrozoan Podocoryne carnea was analysed to evaluate the role of this conserved gene familiy at the base of animal evolution. Surprisingly, the proteinase domain of Podocornyne PMP1 is more similar to human meprin than to HMP1 from another hydrozoan, the freshwater polyp Hydra vulgaris. However, PMP1 and HMP1 both contain a small C-terminal domain with six cysteines that distinguishes them from other astacin-like molecules. Similar domains have been described only recently from sea anemone toxins specific for potassium channels. This toxin homology (Tox1) domain is clearly distinct from epidermal growth factor (EGF)-like domains or other cysteine-rich modules and terminates with the characteristic pattern CXXXCXXC with three out of six cysteines in the last eight residues of the protein. PMP1 is transiently expressed at various sites of morphogenetic activity during medusa bud development. In the adult medusa, however, expression is concentrated to the manubrium, the feeding organ, where the PMP1 gene is highly induced upon feeding. These disparate expression patterns suggest a dual role of PMP1 comparable to tolloid in development and, like astacin in the crayfish, also for food digestion. The Tox1 domain of PMP1 could serve as a toxin to keep the pray paralysed after ingestion, but as a sequence module such Tox1 domains with six cysteines are neither restricted to cnidarians nor to toxins.

Amino Acid Sequence↗