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Query: UNIPROT:P06889 (Mol)
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Erwinia chrysanthemi mutants (designated as pecS) displaying derepressed pectate lyase and cellulase synthesis were isolated. In addition, the pecS mutation is responsible for production of an extracellular insoluble blue pigment whose synthesis is cryptic in the wild-type 3937 strain. Transduction analysis indicates that the phenotype is due to a single mutation located near the xyl marker on the strain 3937 chromosome. This mutation was complemented by an R-prime plasmid carrying the xyl and argG genes of E. chrysanthemi, suggesting that the pecS product acts in trans to modulate pectinase, cellulase and blue pigment production. Insertion mutagenesis of the cloned region and recombination of the corresponding mutations in the bacterial chromosome by marker exchange revealed the existence of two divergently transcribed genes, pecS and pecM, that are both involved in the pectate lyase and cellulase regulation. The nucleotide sequences of pecS and pecM were determined. The pecS gene encodes a 166 amino acid polypeptide that shows similarity to the MprA regulatory protein of Escherichia coli whereas the pecM gene encodes a 297 amino acid polypeptide that was shown to be an integral membrane protein. The possible functions of the PecS and PecM proteins derived from the mutant phenotype and sequence analysis are discussed in terms of signal transduction and transcription regulation.
Mol Microbiol 1994 Mar
PMID:pecS: a locus controlling pectinase, cellulase and blue pigment production in Erwinia chrysanthemi. 802 82

The DNA sequence of the regulatory region and the structural gene, nrfA, for cytochrome c552 of Escherichia coli K-12 have been reported. We have now established that nrfA is the first gene in a seven-gene operon, designated the nrf operon, at least five of which are essential for formate-dependent nitrite reduction to ammonia. This operon terminates just upstream of the previously sequenced gltP gene encoding a sodium-independent, glutamate and aspartate transporter. Expression of lac fused to nrfA, nrfE or nrfG is regulated by oxygen repression, FNR-dependent anaerobic induction, nitrite induction and nitrate repression during anaerobic growth, exactly as previously reported for the nrfA promoter. In contrast, expression of the gltP-lac fusion was FNR-independent. The open reading frame immediately downstream of nrfA encodes NrfB, a hydrophilic, penta-haem cytochrome c with an M(r) of 20,714. The structure of the N-terminal region is typical of a signal peptide for a periplasmic protein: cleavage at the putative signal peptide cleavage site, Ala-26, would result in a periplasmic cytochrome with a molecular mass of 18 kDa. The NrfC polypeptide, M(r) 24,567, contains 16 cysteine residues arranged in four clusters typical of the CooF super-family of non-haem iron-sulphur proteins. The NrfD sequence predicts a 318-residue hydrophobic protein with a distribution of acidic and basic amino acids which suggests that NrfD is an integral transmembrane protein with loops in both the periplasm and the cytoplasm. Proteins most similar to NrfD include the PsrC subunit of polysulphide reductase from Wolinella, but, as seven of the 10 most similar proteins are NADH-ubiquinone oxidoreductases, we propose that NrfD participates in the transfer of electrons from the quinone pool into the terminal components of the Nrf pathway. NrfE, M(r) 60,851, is predicted to be another hydrophobic, integral membrane protein homologous to the CdI1 protein of Rhodobacter capsulatus, which has been implicated in the assembly of periplasmic c-type cytochromes. The sequence of the 127 residue NrfF polypeptide, M(r) 14,522, is strikingly similar to the CcI2 protein of R. capsulatus, especially in the putative haem-binding motif, RCPQCQNQN.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Microbiol 1994 Apr
PMID:A seven-gene operon essential for formate-dependent nitrite reduction to ammonia by enteric bacteria. 805 35

We report the characterization of the msbA gene, isolated as a multicopy suppressor of the HtrB temperature-sensitive phenotype. The msbA gene maps to 20.5 min on the Escherichia coli genetic map and encodes a protein with an estimated molecular mass of 64,460 Da, with the properties of an integral membrane protein. The amino acid sequence of MsbA is very similar to those of the family of ATP-dependent translocators, which includes the haemolysin B protein of E. coli and the mammalian multidrug resistance (MDR) proteins. Mutational analysis of msbA indicates that it may form an operon with a downstream gene, orfE, and that both of these genes are essential for bacterial viability under all growth conditions tested.
Mol Microbiol 1993 Jan
PMID:The essential Escherichia coli msbA gene, a multicopy suppressor of null mutations in the htrB gene, is related to the universally conserved family of ATP-dependent translocators. 809 80

The Bacillus subtilis flhA gene lies in the major che/fla operon, a transcription unit that spans 26 kilobases (kb) of DNA. flhA encodes a 677-amino-acid polypeptide that is a strong candidate for an integral membrane protein. The sequence of FlhA displays substantial homology to a newly identified family of putative signal-transducing receptors that have been implicated in diverse cellular processes. FlhA is the first member of this family to be described from a Gram-positive bacterium. We demonstrate that flhA is a flagellar gene and that FlhA is required in trans for the formation of products from some, but not all, B. subtilis motility-related operons that are regulated by the sigma D form of RNA polymerase. We suggest that FlhA is a component of a signalling system that is involved with the formation of some flagellar gene products during the biosynthesis of the flagellum.
Mol Microbiol 1993 Mar
PMID:Bacillus subtilis FlhA: a flagellar protein related to a new family of signal-transducing receptors. 809 15

Invasion of human erythrocytes by Plasmodium falciparum is inhibited by chymostatin. This suggests that digestion of erythrocyte surface proteins by a protease with chymotrypsin-like activity may be involved in the invasion process. We find that treatment of intact erythrocytes with chymotrypsin cleaves the integral membrane protein, band 3, generating a major fragment with an apparent molecular weight of 58 kDa. We have used measurements of the rotational mobility of band 3, labelled with the phosphorescence probe, eosin-5-maleimide, as a monitor of the changes in the molecular organisation of the erythrocyte membrane which accompany band 3 cleavage. We report that the chymotrypsin treatment increases the rotational freedom of band 3, possibly due to conformational changes which disrupt its interaction with the underlying peripheral membrane proteins. We also show that chymotrypsin-treated erythrocytes undergo extensive endocytosis upon incorporation of exogenous fluorescently labelled phospholipid. We suggest that during the invasion process, digestion of band 3 by a chymotrypsin-like protease may induce a localised disruption of the erythrocyte membrane. This destabilised region of membrane may represent the site for the insertion of parasite-derived phospholipid, thus allowing the formation of the parasitophorous vacuole membrane.
Mol Biochem Parasitol 1993 Dec
PMID:Proteolytic digestion of band 3 at an external site alters the erythrocyte membrane organisation and may facilitate malarial invasion. 813 16

Monoclonal antibody 4E9, which was raised against a partially purified detergent extract of rat caudal epididymal sperm, recognizes the tail of sperm from the cauda, but not from caput epididymidis, as well as epithelial cells in a restricted region of the distal caput/corpus epididymidis and proteins in epididymal fluid from corpus and cauda epididymidis. The antigen is apparently a glycoprotein, since it is retained on a Ricinus communis agglutinin I lectin column. Epididymal fluid antigens have apparent M(rs) of 38-26 kD, whereas the membrane-associated form of the molecule has an M(r) of 26 kD. Immunocytochemical data and Western immunoblot data suggest that the membrane antigen is derived from the fluid antigen, which, in turn, is secreted by the epididymal epithelium. Characterization of the membrane antigen indicates that it is tightly associated with the sperm surface, behaving as though it is an integral membrane protein. The antigen persists on ejaculated sperm.
Mol Reprod Dev 1994 Feb
PMID:Rat epididymis-specific sperm maturation antigens. I. Evidence that the 26 kD 4E9 antigen found on rat caudal epididymal sperm tail is derived from a protein secreted by the epididymis. 817 1

We have previously identified and characterized an integral membrane protein coded for by the early transcription region 3 (E3) of human group C adenoviruses that down-regulates the epidermal growth factor receptor (EGFR). The goal of this study was to characterize the early receptor trafficking events leading to enhanced EGFR degradation in adenovirus-infected cells. Specifically, we wished to determine whether adenovirus increases the rate of EGFR internalization or alters the subcellular compartmentalization of internalized EGFRs. Once the optimal time for measuring early trafficking events was determined, surface EGFRs were labeled with a cleavable biotin reagent to measure internalization rates and with a receptor-specific monoclonal antibody (MAb) conjugated to colloidal gold for intracellular localization studies. We first showed that the rate of EGFR internalization in adenovirus-infected cells is indistinguishable from the constitutive internalization rate for unoccupied EGFRs. The possibility that the E3 protein can affect trafficking of EGFRs internalized at a low constitutive rate was further supported by studies showing that adenovirus-mediated down-regulation occurs independently of EGFR oligomerization and intrinsic EGFR tyrosine kinase activity, which are required for efficient ligand-induced internalization. Other tyrosine kinases inhibited by genistein are also not required for adenovirus-induced down-regulation. When the intracellular localization of EGFRs during adenovirus-mediated down-regulation was examined by electron microscopy, there was a threefold increase in the number of EGFRs localized to multivesicular bodies. The multivesicular body has been proposed to be important for regulating intracellular membrane protein sorting, since trafficking patterns for receptors that recycle and receptors that are degraded diverge in this organelle. These data therefore suggest that adenovirus may enhance EGFR degradation by causing constitutively internalized EGFRs to accumulate in a prelysosomal compartment. This is the first example of a mechanism that efficiently down-regulates EGFR without significantly increasing the rate of internalization or that does not require EGFR tyrosine kinase activity. Since viral proteins often mimic or modify a host counterpart, this suggests that there are normal physiological conditions when receptor destruction without tyrosine signalling is beneficial.
Mol Cell Biol 1994 Jun
PMID:Adenovirus E3 protein causes constitutively internalized epidermal growth factor receptors to accumulate in a prelysosomal compartment, resulting in enhanced degradation. 819 13

Characterization of the genes involved in the process of protein translocation is important in understanding their structure-function relationships. However, little is known about the signals that govern chlamydial gene expression and translocation. We have cloned a 1.7 kb HindIII-PstI fragment containing the secY gene of Chlamydia trachomatis. The complete nucleotide sequence reveals three open reading frames. The amino acid sequence shows highest homology with Escherichia coli proteins L15, SecY and S13, corresponding to the spc-alpha ribosomal protein operons. The product of the C. trachomatis secY gene is composed of 457 amino acids with a calculated molecular mass of 50,195 Daltons. Its amino acid sequence shows 27.4% and 35.7% identity to E. coli and Bacillus subtilis SecY proteins, respectively. The distribution of hydrophobic amino acids in the C. trachomatis secY gene product is suggestive of it being an integral membrane protein with ten transmembrane segments, the second, third and seventh membrane segments sharing > 45% identity with E. coli SecY. Our results suggest that despite evolutionary differences, eubacteria share a similar protein export apparatus.
Mol Gen Genet 1994 May 25
PMID:Cloning and characterization of a secY homolog from Chlamydia trachomatis. 820 93

The L-rhamnose-H+ symporter (RhaT) is a 344-amino acid integral membrane protein, found in many Enterobacteria, which couples the uptake of the sugar L-rhamnose with the inward movement of protons. Based on its hydropathy profile and the application of von Heijne's "positive inside" rule (von Heijne, G. (1992) J. Mol. Biol. 225, 487-494), a model of the L-rhamnose-H+ symport protein (RhaT) is proposed containing 10 transmembrane helices with the NH2 and COOH termini in the periplasm. This model was tested by the creation of random beta-lactamase (Bla) fusions. The data from 33 unique, randomly generated, RhaT-Bla fusions and from 5 site-specific fusions supported the proposed topology between transmembrane helices 2-10. However, the localization of the putative first hydrophilic loop and the NH2 terminus was not possible because the beta-lactamase fusions in this region were shown to be unreliable indicators of the topology of RhaT.
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PMID:Membrane topology of the L-rhamnose-H+ transport protein (RhaT) from enterobacteria. 826 18

The Na+/H+ exchanger is an integral membrane protein that is universally distribute in mammalian tissues and is responsible for intracellular pH regulation. Several isoforms of the Na+/H+ exchanger exist (NHE-1-NHE-4). The first that was cloned is the amiloride sensitive isoform (NHE-1). Using a fragment of the rabbit cardiac Na+/H+ exchanger cDNA clone we isolated and sequenced Na+/H+ exchanger cDNA from a human heart coding for the complete human Na+/H+ exchanger (NHE-1 isoform). Two overlapping cDNA clones were obtained, giving a combined sequence that contained both 3' and 5' untranslated regions. The 5' and 3' untranslated regions proved to be highly homologous to human sequences described earlier but contained some variations that could affect the mRNA stability and/or the efficiency of translation of the Na+/H+ exchanger. Northern blot analysis and reverse transcriptase polymerase chain reaction confirmed the presence of the 5 kb NHE-1 message in primary cultures of isolated myocytes.
Mol Cell Biochem 1993 Aug 25
PMID:Cloning and analysis of the human myocardial Na+/H+ exchanger. 828 68


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