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At least 703 records · Page 39Linked to original sources
PubMed2004

NolR regulates diverse symbiotic signals of Sinorhizobium fredii HH103.

We have investigated in Sinorhizobium fredii HH103-1 (=HH103 Str(r)) the influence of the nolR gene on the production of three different bacterial symbiotic signals: Nod factors, signal responsive (SR) proteins, and exopolysaccharide (EPS). The presence of multiple copies of nolR (in plasmid pMUS675) repressed the transcription of all the flavonoid-inducible genes analyzed: nodA, nodD1, nolO, nolX, noeL, rhcJ, hesB, and y4pF. Inactivation of nolR (mutant SVQ517) or its overexpression (presence of pMUS675) altered the amount of Nod factors detected. Mutant SVQ517 produced Nod factors carrying N-methyl residues at the nonreducing N-acetyl-glucosamine, which never have been detected in S. fredii HH103. Plasmid pMUS675 increased the amounts of EPS produced by HH103-1 and SVQ517. The flavonoid genistein repressed EPS production of HH103-1 and SVQ517 but the presence of pMUS675 reduced this repression. The presence of plasmid pMUS675 clearly decreased the secretion of SR proteins. Inactivation, or overexpression, of nolR decreased the capacity of HH103 to nodulate Glycine max. However, HH103-1 and SVQ517 carrying plasmid pMUS675 showed enhanced nodulation capacity with Vigna unguiculata. The nolR gene was positively identified in all S. fredii strains investigated, S. xinjiangense CCBAU110, and S. saheli USDA4102. Apparently, S. teranga USDA4101 does not contain this gene.

Bacterial Proteins↗
PubMedDate not supplied

Specific milk immune response of rural and urban Guatemalan women to oral immunization with a food protein.

Forty-nine lactating women from Guatemala, 18 from a rural community and 31 from Guatemala City, were immunized orally with a protein extract from Vigna sinensis. Oral vaccination during the 1st week postpartum induced the appearance of short-lived, specific antibodies in milk in 59% of the subjects. No differences in rates of lactoconvertion were found either between socioeconomic groups or between malnourished and well-nourished women.

Adult↗
PubMed1993

Failure of long-distance movement of southern bean mosaic virus in a resistant host is correlated with lack of normal virion formation.

Sunn-hemp mosaic tobamovirus (SHMV) facilitated the spread of the cowpea strain of southern bean sobemovirus (SBMV-C) only in inoculated leaves of common bean (Phaseolus vulgaris L. cv. Bountiful), a resistant host for SBMV-C. Tissue prints of bean primary leaves doubly inoculated with SHMV and SBMV-C, developed by Western blotting, showed the presence of the SBMV-C capsid antigen in the mesophyll and epidermis, but no antigen was detected in the conducting bundles. Typical SBMV-C virions were not seen in electron micrographs of immunogold-labelled mesophyll cells; instead, specifically labelled, amorphous protein clumps were found in the vacuole. Particles of smaller diameter than that of typical SBMV-C virions were specifically trapped by SBMV antibodies following immunosorbent electron microscopy of extracts from doubly infected leaves. SBMV-C coat protein from infected Vigna unguiculata L. (cowpea) and bean plants showed no difference in its mobility following electrophoresis in denaturing SDS-polyacrylamide gels. Lack of efficient assembly of SBMV-C virions does not impede cell-to-cell movement of the virus in doubly infected leaves of bean, yet it is probably an important factor in determining the inability of SBMV-C to move into and/or through the vascular system of this host.

Antigens, Viral↗
PubMed1997

A protoplast system for studying tomato spotted wilt virus infection.

A plant protoplast system for studying tomato spotted wilt tospovirus (TSWV) infection was established and tested. Using polyethylene glycol-mediated inoculation with highly infectious TSWV particles, generally 50% or more of Nicotiana rustica protoplasts were infected. In these cells viral RNA and viral protein synthesis became detectable at 16 h post-inoculation (p.i.) and continued at least until 90 h p.i. Both the structural viral proteins [nucleoprotein (N) and the envelope glycoproteins G1 and G2] and the nonstructural viral proteins NSs and NSm accumulated to amounts sufficient for detection and immunocytological analysis. Local lesion tests on petunia leaves and electron microscopical analysis confirmed the production of mature, infectious virus particles, underlining the conclusion that a full infection cycle was completed in this system. Upon inoculation of Vigna unguiculata (cowpea) protoplasts with TSWV particles, comparable proportions of infected cells and amounts of NSs, NSm and N protein were obtained, but much lower amounts of viral glycoproteins were detected than in N. rustica protoplasts, and progeny virus particles were less abundant. With the N. rustica-based protoplast system, a powerful synchronized single-cell infection system has now become available for more precise in vivo studies of the processes occurring during tospovirus infection.

Animals↗
PubMed1996

Proline biosynthesis in Streptococcus thermophilus: characterization of the proBA operon and its products.

The presence of proline in the medium was not essential for growth of Streptococcus thermophilus, indicating that there is a proline biosynthetic pathway in this organism. Genetic and biochemical analysis identified and characterized this pathway. Two genes, designated proB and proA, were cloned, sequenced and characterized. Biochemical analysis of the proB- and proA-encoded enzymes showed that the proline biosynthetic pathway of S. thermophilus is similar to the one previously described in Escherichia coli. The deduced amino acid sequence of a 2-408 kb DNA region containing the genes revealed the similarity of the S. thermophilus gene products to ProB and ProA of E. coli and Serratia marcescens, and to the corresponding N- and C-terminal domains of the bifunctional plant enzyme delta 1-pyrroline-5-carboxylate synthetase of Vigna aconitifolia. Northern blot analysis showed that the two genes in S. thermophilus are organized in a single operon with proB proximal and proA distal to the promoter; primer extension analysis indicated that proBA transcription is not under repressive control by exogenously supplied proline.

Aldehyde Oxidoreductases↗
PubMed2005

Coat proteins of Rice tungro bacilliform virus and Mungbean yellow mosaic virus contain multiple nuclear-localization signals and interact with importin alpha.

Transport of the viral genome into the nucleus is an obligatory step in the replication cycle of plant pararetro- and geminiviruses. In both these virus types, the multifunctional coat protein (CP) is thought to be involved in this process. Here, a green fluorescent protein tagging approach was used to demonstrate nuclear import of the CPs of Rice tungro bacilliform virus (RTBV) and Mungbean yellow mosaic virus--Vigna (MYMV) in Nicotiana plumbaginifolia protoplasts. In both cases, at least two nuclear localization signals (NLSs) were identified and characterized. The NLSs of RTBV CP are located within both N- and C-terminal regions (residues 479KRPK/497KRK and 744KRK/758RRK), and those of MYMV CP within the N-terminal part (residues 3KR and 41KRRR). The MYMV and RTBV CP NLSs resemble classic mono- and bipartite NLSs, respectively. However, the N-terminal MYMV CP NLS and both RTBV CP NLSs show peculiarities in the number and position of basic residues. In vitro pull-down assays revealed interaction of RTBV and MYMV CPs with the nuclear import factor importin alpha, suggesting that both CPs are imported into the nucleus via an importin alpha-dependent pathway. The possibility that this pathway could serve for docking of virions to the nucleus is discussed.

Capsid Proteins↗
PubMed2002

Cloning and characterization of the abscisic acid-specific glucosyltransferase gene from adzuki bean seedlings.

The glycosylated forms of abscisic acid (ABA) have been identified from many plant species and are known to be the forms of ABA-catabolism, although their (physiological) roles have not yet been elucidated. ABA-glucosyltransferase (-GTase) is thought to play a key role in the glycosylation of ABA. We isolated an ABA-inducible GTase gene from UDP-GTase homologs obtained from adzuki bean (Vigna angularis) seedlings. The deduced amino acid sequence (accession no. AB065190) showed 30% to 44% identity with the known UDP-GTase homologs. The recombinant protein with a glutathione S-transferase-tag was expressed in Escherichia coli and showed enzymatic activity in an ABA-specific manner. The enzymatic activity was detected over a wide pH range from 5.0 to 9.0, the optimum range being between pH 6.0 and 7.3, in a citrate and Tris-HCl buffer. The product from racemic ABA and UDP-D-glucose was identified to be ABA-GE by gas chromatography/mass spectrometry. The recombinant GTase (rAOG) converted 2-trans-(+)-ABA better than (+)-S-ABA and (-)-R-ABA. Although trans-cinnamic acid was slightly converted to its conjugate by the GTase, (-)-PA was not at all. The mRNA level was increased by ABA application or by water stress and wounding. We suggest that the gene encodes an ABA-specific GTase and that its expression is regulated by environmental stress.

Abscisic Acid↗
PubMed2002

Distinct N-terminal regulatory domains of Ca(2+)/H(+) antiporters.

The regulation of intracellular Ca(2+) levels is achieved in part by high-capacity vacuolar Ca(2+)/H(+) antiporters. An N-terminal regulatory region (NRR) on the Arabidopsis Ca(2+)/H(+) antiporter CAX1 (cation exchanger 1) has been shown previously to regulate Ca(2+) transport by a mechanism of N-terminal auto-inhibition. Here, we examine the regulation of other CAX transporters, both within Arabidopsis and from another plant, mung bean (Vigna radiata), to ascertain if this mechanism is commonly used among Ca(2+)/H(+) antiporters. Biochemical analysis of mung bean VCAX1 expressed in yeast (Saccharomyces cerevisiae) showed that N-terminal truncated VCAX1 had approximately 70% greater antiport activity compared with full-length VCAX1. A synthetic peptide corresponding to the NRR of CAX1, which can strongly inhibit Ca(2+) transport by CAX1, could not dramatically inhibit Ca(2+) transport by truncated VCAX1. The N terminus of Arabidopsis CAX3 was also shown to contain an NRR. Additions of either the CAX3 or VCAX1 regulatory regions to the N terminus of an N-terminal truncated CAX1 failed to inhibit CAX1 activity. When fused to N-terminal truncated CAX1, both the CAX3 and VCAX1 regulatory regions could only auto-inhibit CAX1 after mutagenesis of specific amino acids within this NRR region. These findings demonstrate that N-terminal regulation is present in other plant CAX transporters, and suggest distinct regulatory features among these transporters.

Amino Acid Sequence↗
PubMed2002

Effect of short-term N(2) deficiency on expression of the ureide pathway in cowpea root nodules.

Root systems of 28-d-old cowpea (Vigna unguiculata L. Walp cv Vita 3: Bradyrhizobium sp. strain CB756) plants bearing nitrogen-fixing nodules in sand culture were exposed to an atmosphere of Ar:O(2) (80:20, v/v) for 48 h and then returned to air. Root systems of control plants were maintained in air throughout. Nodules were harvested at the same times in control and Ar:O(2)-treated root systems. Activities of two enzymes of de novo purine synthesis, glycinamide ribonucleotide transformylase (GART; EC 2.1.2.2), aminoimidazole ribonucleotide synthetase (AIRS; EC 6.3.3.1), uricase (EC 1.7.3.3), and phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) were measured together with the protein level of each using immune-specific polyclonal antibodies. AIRS activity and protein both declined to very low levels within 6 h in Ar:O(2) together with a decline in transcript level of pur5, the encoding gene. GART activity, protein, and transcript (pur3) levels were relatively stable. Uricase activity declined in Ar:O(2) as rapidly as AIRS activity but the protein was stable. PEPC activity showed evidence of increased sensitivity to inhibition by malate but the protein level was stable. The data indicate that the flux of fixed N from bacteroids (N(2)-fixing nodule bacteria) is in some way associated with transcriptional control over pur5 and possibly also catabolism of AIRS protein. In contrast, there is limited posttranslational control over GART and PEPC and close posttranslational control over uricase activity. The significance of these different levels of regulation is discussed in relation to the overall control of enhanced expression of plant enzymes in the cowpea symbiosis.

Argon↗
PubMed1992

Mechanism of the Decline in Vacuolar H -ATPase Activity in Mung Bean Hypocotyls during Chilling.

The mechanism responsible for the decrease in the activity of vacuolar H(+) -ATPase during chilling was investigated in seedlings of mung bean (Vigna radiata). After chilling at 0 degrees C for 3 d, the activity of vacuolar H(+) -ATPase, calculated on the basis of membrane protein, decreased to 47% of the original value. Of the nine subunits of the ATPase, the specific contents of at least six subunits, of 68, 57, 44, 38, 37, and 32 kD, decreased in vacuolar membranes after chilling, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These subunits were released by treatment with chaotropic anions such as thiocyanate. The level of the 16-kD subunit did not change. Immunoblot analyses showed the decrease in the levels of the subunits of 68, 57, and 32 kD. Furthermore, the specific activity of the ATPase purified from chilled hypocotyls was two-thirds of that of the enzyme from nonchilled seedlings, and the enzyme from chilled tissue retained only a small amount of the 32-kD subunit. These results suggest that a selective release of the peripheral subunits of the ATPase from the membrane and a partial degradation of the ATPase complex may occur in vivo during chilling.

Journal Article↗
PubMed1992

Gibberellins and the Legume-Rhizobium Symbiosis : III. Quantification of Gibberellins from Stems and Nodules of Lima Bean and Cowpea.

Lima bean (Phaseolus lunatus L.) plants inoculated with Bradyrhizobium sp. strain 127E14 displayed a period of marked internode elongation that was not observed in plants inoculated with other compatible bradyrhizobia, including strain 127E15. When strain 127E14 nodulated an alternate host, cowpea (Vigna unguiculata L. Walp), a similar, although less dramatic growth response induced by the bacteria was observed. It has been speculated that the elongative growth promotion brought about by inoculation with strain 127E14 is mediated by gibberellins (GAs). Using deuterated internal standards and gas chromatography-mass spectroscopy analysis, we have quantified the levels of GA(1), GA(20), GA(19), and GA(44) in nodules and stems of two varieties of lima bean (bush and pole) and one variety of cowpea that were inoculated with either strain 127E14 or 127E15. In nodules formed by strain 127E14 on lima bean, endogenous levels of GA(20) and GA(19) were 10 to 40 times higher (35-88 ng/g dry weight) than amounts found in nodules formed by strain 127E15 (2.2-3.9 ng/g dry weight). Relative amounts of GA(44) were also higher (4- to 11-fold) in 127E14 nodules, but this increase was less pronounced. The rhizobial-induced increase of these GAs in the nodule occurred in both pole and bush varieties and seemed to be independent of host morphology. Regardless of rhizobial inoculum, levels of the "bioactive" GA(1) in the nodule (0.3-1.1 ng/g dry weight) were similar. In cowpea nodules, a similar, although smaller, difference in GA content due to rhizobial strain was observed. The concentration of GA(1) in lima bean stems was generally higher than that observed in the nodule, whereas concentrations of the other GAs measured were lower. In contrast with the nodule, GA concentrations in lima bean stems were not greater in plants inoculated with strain 127E14, and in some cases the slower growing plants inoculated with strain 127E15 actually had higher levels of GA(20), GA(19), and GA(44). Thus, there were major differences in concentrations of the precursors to GA(1) in nodules formed by the two bacterial strains, which were positively correlated with the observed elongation growth. These results support the hypothesis that the rhizobial strain modifies the endogenous GA status of the symbiotic system. This alteration in GA balance within the plant, presumably, underlies the observed growth response.

Journal Article↗
PubMed1992

Purification and characterization of 1-aminocyclopropane-1-carboxylate N-malonyltransferase from etiolated mung bean hypocotyls.

1-Aminocyclopropane-1-carboxylate (ACC) N-malonyltransferase converts ACC, an immediate precursor of ethylene, to the presumably inactive product malonyl-ACC (MACC). This enzyme plays a role in ethylene production by reducing the level of free ACC in plant tissue. In this study, ACC N-malonyltransferase was purified 3660-fold from etiolated mung bean (Vigna radiata) hypocotyls, with a 6% overall recovery. The final specific activity was about 83,000 nmol of MACC formed mg(-1) protein h(-1). The five-step purification protocol consisted of polyethylene glycol fractionation, Cibacron blue 3GA-agarose chromatography using salt gradient elution, Sephadex G-100 gel filtration, MonoQ anion-exchange chromatography, and Cibacron blue 3GA-agarose chromatography using malonyl-CoA plus ACC for elution. The molecular mass of the native enzyme determined by Sephadex G-100 chromatography was 50 +/- 3 kD. Protein from the final purification step showed one major band at 55 kD after sodium dodecyl sulfate polyacrylamide gel electrophoresis, indicating that ACC N-malonyltransferase is a monomer. The mung bean ACC N-malonyltransferase has a pH optimum of 8.0, an apparent K(m) of 0.5 mm for ACC and 0.2 mm for malonyl-coenzyme A, and an Arrhenius activation energy of 70.29 kJ mol(-1) degree(-1).

Journal Article↗
PubMed1993

Identification of a basic glycoprotein induced by ethylene in primary leaves of azuki bean as a cationic peroxidase.

Ethylene causes the accumulation of seven different proteins (each designated AZxx according to its molecular mass, xx in kD) in excised primary leaves of azuki bean (Vigna angularis) (F. Ishige, H. Mori, K. Yamazaki, H. Imaseki [1991] Plant Cell Physiol 32: 681-690). A complementary DNA encoding an ethylene-induced basic glycoprotein, AZ42, from azuki bean was cloned and its complete nucleotide sequence was determined. Characterization of the cDNA was accomplished by monitoring expression of an immunoreactive protein in Escherichia coli that harbored the cDNA and by the identification of a partial amino acid sequence that was the same as that determined from the purified protein. An open reading frame (1071 base pairs) in the cDNA encoded a protein of 357 amino acids with a molecular mass of 39.3 kD. The amino acid sequence contained three regions that are highly conserved among peroxidases from eight different plants. Purified AZ42 exhibited peroxidase activity. The basic glycoprotein induced by ethylene was identified as a cationic isozyme of peroxidase. The corresponding mRNA was not present in leaves that had not been treated with ethylene, but it appeared after 1 h of treatment with ethylene and its level increased for the next 15 h. Accumulation of the mRNA was also induced after wounding or treatment with salicylate. The wound-induced increase in the level of the mRNA was suppressed by 2,5-norbornadiene, but the salicylate-induced increase was not.

Amino Acid Sequence↗
PubMed1993

Expression of an Endopeptidase (EP-C1) in Phaseolus vulgaris Plants.

Endopeptidase activity increases continually in pods of maturing fruits of French bean (Phaseolus vulgaris L. cv Goldstar) plants and is thought to participate in the protein mobilization in pods during the development of seeds (M. Endo, T. Minamikawa, D. Yamauchi, W. Mitsuhashi [1987] J Exp Bot 38: 1988-1995). In the present studies, one of the major endopeptidase forms, designated EP-C1, was purified as a 34-kD polypeptide from pods of maturing French bean fruits. EP-C1 was found to be immunologically distinguished from other forms in extracts from pods, but homologous to SH-EP, the major cysteine endopeptidase expressed in cotyledons of germinating Vigna mungo seeds (W. Mitsuhashi, T. Minamikawa [1989] Plant Physiol 89: 274-279). The level of endopeptidase that reacted with the antiserum to EP-C1 increased in pods as the fruit maturation proceeded. EP-C1 was also immunologically detected in stems of French bean plants bearing fruits of later maturation stages. Protein immunoblotting showed that a 34-kD polypeptide corresponding to EP-C1 in molecular mass occurred in extracts from 7- to 9-d cotyledons of germinating French bean seeds. In addition, two other polypeptides with slightly higher molecular masses were observed in extracts from 3- to 5-d cotyledons. We suggest that these two polypeptides are intermediates involved in posttranslational processing of EP-C1. RNA blot hybridization with EP-C1 cDNA as a probe showed that EP-C1 mRNA occurred in pods of fruits at later maturing stages and also in cotyledons of 3- to 7-d germinating seeds.

Journal Article↗
PubMed2003

Dual intracellular localization and targeting of aminoimidazole ribonucleotide synthetase in cowpea.

De novo purine biosynthesis is localized to both mitochondria and plastids isolated from Bradyrhizobium sp.-infected cells of cowpea (Vigna unguiculata L. Walp) nodules, but several of the pathway enzymes, including aminoimidazole ribonucleotide synthetase (AIRS [EC 6.3.3.1], encoded by Vupur5), are encoded by single genes. Immunolocalization confirmed the presence of AIRS protein in both organelles. Enzymatically active AIRS was purified separately from nodule mitochondria and plastids. N-terminal sequencing showed that these two isoforms matched the Vupur5 cDNA sequence but were processed at different sites following import; the mitochondrial isoform was five amino acids longer than the plastid isoform. Electrospray tandem mass spectrometry of a trypsin digest of mitochondrial AIRS identified two internal peptides identical with the amino acid sequence deduced from Vupur5 cDNA. Western blots of proteins from mitochondria and plastids isolated from root tips showed a single AIRS protein present at low levels in both organelles. (35)S-AIRS protein translated from a Vupur5 cDNA was imported into isolated pea (Pisum sativum) leaf chloroplasts in vitro by an ATP-dependent process but not into import-competent mitochondria from several plant and non-plant sources. Components of the mature protein are likely to be important for import because the N-terminal targeting sequence was unable to target green fluorescent protein to either chloroplasts or mitochondria in Arabidopsis leaves. The data confirm localization of the protein translated from the AIRS gene in cowpea to both plastids and mitochondria and that it is cotargeted to both organelles, but the mechanism underlying import into mitochondria has features that are yet to be identified.

Amino Acid Sequence↗
PubMed2003

Solubilization of an arabinan arabinosyltransferase activity from mung bean hypocotyls.

The biosynthesis of polysaccharides destined for the plant cell wall and the subsequent assembly of the cell wall are poorly understood processes that are currently the focus of much research. Arabinan, a component of the pectic polysaccharide rhamnogalacturonan I, is composed of arabinosyl residues connected via various glycosidic linkages, and therefore, the biosynthesis of arabinan is likely to involve more than one arabinosyltransferase. We have studied the transfer of [(14)C]arabinose (Ara) from UDP-L-arabinopyranose onto polysaccharides using microsomal membranes isolated from mung bean (Vigna radiata) hypocotyls. [(14)C]arabinosyl and [(14)C]xylosyl residues were incorporated into endogenous products due to the presence of UDP-Xyl-4-epimerase activity. Enzymatic digestion of endogenous products with endo-arabinanase released very little radiolabeled sugars, whereas digestion with arabinofuranosidase released some [(14)C]Ara. Microsomal membranes solubilized with the detergent octyl glucoside were able to add a single [(14)C]Ara residue onto (1-->5)-linked alpha-L-arabino-oligosaccharide acceptors. The reaction had a pH optimum of 6.5 and a requirement for manganese ions. However, enzymatic digestion of the radiolabeled oligosaccharides with endo-arabinanase and arabinofuranosidases could not fully release the radiolabeled Ara residue, indicating that the [(14)C]Ara residue was not a (1-->2)-, (1-->3)-, or (1-->5)-linked alpha-L-arabinofuranosyl residue. Rather, mild acid treatment of the product suggested that the radiolabeled Ara residue was in a pyranose conformation, and this result was confirmed by thin-layer chromatography of radiolabeled partially methylated sugars. Using microsomal membranes separated on a discontinuous sucrose gradient, the arabinosyltransferase activity appears to be mainly localized to Golgi membranes.

Arabinose↗
PubMed1993

Molecular heterogeneity of photosystem I. psaD, psaE, psaF, psaH, and psaL are all present in isoforms in Nicotiana spp.

The protein composition of photosystem I (PSI) was examined in Nicotiana spp. by high-resolution polyacrylamide gel electrophoresis, N-terminal amino acid sequencing, and immunoblot analysis. Five PSI proteins show polymorphism in an amphidiploid species, Nicotiana tabacum, but not in its ancestral diploid species, Nicotiana sylvestris and Nicotiana tomentosiformis. These Nicotiana spp. appear to have at least 18 PSI proteins per genome that range in molecular mass from 3 to 20 kD. They include the products of nuclear genes psaD, psaE, psaF, psaG, psaH, psaK, and psaL, the product of chloroplast gene psaC, N-terminally blocked proteins of 4.5 and 3.0 kD, and an unidentified protein of 12.5 kD. The psaD, psaF, psaH, and psaL products have two isoforms each that are distinguished by different mobilities in polyacrylamide gel electrophoresis, and the psaE product has four isoforms. The two isoforms of the psaD product have distinct amino acid sequences, indicating that they are encoded by different genes within the genome. Four isoforms of the psaE products can be classified into two groups by N-terminal amino acid sequence, indicating that at least two psaE genes are present in the genome. To examine whether the polymorphic nature of PSI is peculiar to Nicotiana spp., we carried out immunoblot analysis of the psaD and psaE products in isogenic lines of tomato (Lycopersicon esculentum), Arabidopsis thaliana, red bean (Vigna angularis), and corn (Zea mays). Two electrophoretically distinct isoforms were found for the psaD products of tomato, A. thaliana, and corn, and two isoforms of psaE products were detected in tomato, A. thaliana, and red bean. These results suggest that the nuclear-encoded subunits of PSI, except for the psaG and psaK products, generally have two isoforms.

Amino Acid Sequence↗
PubMed2003

C-terminal KDEL sequence of a KDEL-tailed cysteine proteinase (sulfhydryl-endopeptidase) is involved in formation of KDEL vesicle and in efficient vacuolar transport of sulfhydryl-endopeptidase.

Sulfhydryl-endopeptidase (SH-EP) is a papain-type vacuolar proteinase expressed in cotyledons of germinated Vigna mungo seeds, and the enzyme possesses a C-terminal propeptide containing KDEL tail, an endoplasmic reticulum retention signal for soluble proteins. SH-EP is transported to vacuoles via a KDEL vesicle (KV) through a Golgi complex-independent route. To see the function of the KDEL sequence of SH-EP, wild-type SH-EP and its KDEL deletion mutant (SH-EPDeltaKDEL) were heterologously expressed in Arabidopsis and in cultured tobacco Bright Yellow 2 cells, and their intracellular transport pathways and localizations were analyzed. A combination of the results from analyses for transformed Arabidopsis and tobacco (Nicotiana tabacum) cells indicated that wild-type SH-EP is packed into KV-like vesicles through the KDEL sequence and is transported to vacuoles in the cells of transformants. In contrast, KV was not formed/induced in the cells expressing SH-EPDeltaKDEL, and the mutant protein was mainly secreted. Therefore, the C-terminal KDEL sequence of the KDEL-tailed cysteine proteinase is thought to be involved in the formation of KV, and in the efficient vacuolar transport of the proteins through KV.

Arabidopsis↗