A gene at 59 minutes on the Escherichia coli chromosome encodes a lipoprotein with unusual amino acid repeat sequences.

We report a 1.432-kb DNA sequence at 59 min on the Escherichia coli chromosome that connects the published sequences of the pcm gene for the isoaspartyl protein methyltransferase and that of the katF or rpoS (katF/rpoS) gene for a sigma factor involved in stationary-phase gene expression. Analysis of the DNA sequence reveals an open reading frame potentially encoding a polypeptide of 379 amino acids. The polypeptide sequence includes a consensus bacterial lipidation sequence present at residues 23 to 26 (Leu-Ala-Gly-Cys), four octapeptide proline- and glutamine-rich repeats of consensus sequence QQPQIQPV, and four heptapeptide threonine- and serine-rich repeats of consensus sequence PTA(S,T)TTE. The deduced amino acid sequence, especially in the C-terminal region, is similar to that of the Haemophilus somnus LppB lipoprotein outer membrane antigen (40% overall sequence identity; 77% identity in last 95 residues). The LppB lipoprotein binds Congo red dye and has been proposed to be a virulence determinant in H. somnus. Utilizing a plasmid construct with the E. coli gene under the control of a phage T7 promoter, we demonstrate the lipidation of this gene product by the incorporation of [3H]palmitic acid into a 42-kDa polypeptide. We also show that treatment of E. coli cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 46-kDa precursor. We thus designate the protein NlpD (new lipoprotein D). E. coli cells overexpressing NlpD bind Congo red dye, suggesting a common function with the H. somnus LppB protein. Disruption of the chromosomal E. coli nlpD gene by insertional mutagenesis results in decreased stationary-phase survival after 7 days.     

Nucleotide sequence and LexA regulation of the Escherichia coli recN gene.

The nucleotide sequence of a 2224 bp region of the Escherichia coli chromosome that carries the LexA regulated recN gene has been determined. A region of 1701 nucleotides encoding a polypeptide of 567 amino acids with a predicted molecular weight of 63,599 was identified as the most probable sequence for the recN structural gene. The proposed initiation codon is preceded by a reasonable Shine-Dalgarno sequence and a promoter region containing two 16 bp sequences, separated by 6 bp, that match the consensus sequence (SOS box) for binding LexA protein. DNA fragments containing this putative promoter region are shown to bind LexA in vitro and to have LexA-regulated promoter activity in vivo. The amino acid sequence of RecN predicted from the DNA contains a region that is homologous to highly conserved sequences found in several DNA repair enzymes and other proteins that bind ATP. A sequence of 9 amino acids was found to be homologous to a region of the RecA protein of E. coli postulated to have a role in DNA/nucleotide binding.     

Cloning and sequence analysis of the gene encoding Lactococcus lactis malolactic enzyme: Relationships with malic enzymes

Abstract Malolactic enzyme is the key enzyme in the degradation of L-malic acid by lactic acid bacteria. Using degenerated primers designed from the first 20 N-terminal amino acid sequence of lactococcal malolactic enzyme, a 60-bp DNA fragment containing part of the mleS gene was amplified from Lactococcus lactis in a polymerase chain reaction. This specific probe was used to isolate two contiguous fragments covering the gene as a whole. The 1.9-kb region sequenced contains an open reading frame of 1623 bp, coding a putative protein of 540 amino acids. The deduced amino acid sequence reveals that lactococcal putative protein (Mlep) is highly homologous to the malic enzyme of other organisms. Expression of the mleS gene in Escherichia coli results in malolactic activity.     

Conserved reiterated domains in Clostridium thermocellum endoglucanases are not essential for catalytic activity

The complete nucleotide sequence of the Clostridium thermocellum celE gene, coding for an endo-beta-1,4-glucanase (endoglucanase E; EGE) with xylan-hydrolysing activity has been determined. The structural gene consists of an open reading frame (ORF) of 2442 bp commencing with a GTG start codon and followed by a TAA stop codon. The nucleotide sequence obtained has been confirmed by comparing the predicted amino acid sequence with that derived by N-terminal amino acid sequencing of the purified protein. The EGE sequence contains a region homologous to the reiterated domain found at the C terminus of other endoglucanases from the same organism. BAL 31 deletions of the structural gene have revealed the extent to which this conserved sequence is necessary for endoglucanase and xylanase activity. A region of DNA, upstream from the structural gene has also been sequenced and a ribosome-binding site and putative promoter sequences have been identified. A second ORF which ends 349 bp 5' to the GTG start codon of the celE gene has also been identified. The encoded product contains a C terminus homologous to other C. thermocellum endoglucanases.     

杧果LEAFY同源基因的分离及序列分析

分析在植物开花过程中起重要作用的LEAFY(LFY)基因的保守区序列,设计1对长度均为23bp的PCR引物,以杧果基因组DNA为模板,采用PCR方法扩增出长为822bp的DNA片段,克隆入pGEM-T Easy载体。测序和序列分析表明,获得了杧果LFY同源基因(miLFY)3’端的1个片段,该片段有1个415bp的内含子,编码区共编码135个氨基酸,其序列已经在GenBank中登记(登录号AY189684)。在GenBank中进行同源性检索,发现其氨基酸序列与其它植物LFY同源基因的氨基酸序列同源性高达74%~97%,推测它们具有相似的功能。     

Structure of a Bacillus subtilis endo-beta-1,4-glucanase gene.

The nucleotide sequence of the portion of a Bacillus subtilis (strain PAP115) 3 kb Pst I fragment which contains an endo-beta-1, 4-glucanase gene has been determined. This gene encodes a protein of 499 amino acid residues (Mr = 55,234) with a typical B. subtilis signal peptide. Escherichia coli which has been transformed with this gene produces an extracellular endoglucanase with an amino-terminus corresponding to the thirtieth encoded amino acid residue. The gene is preceded by a cryptic reading frame with a rho-independent terminator structure, and itself has such a structure in the immediate 3'-flanking region. We have also identified, in the 5'-flanking region, nucleotide sequences which resemble promoter elements recognized by Bacillus RNA polymerase E sigma 43. Comparison of the encoded amino acid sequence to other known beta-glucanases reveals a small region of similarity to the encoded protein of the Clostridium thermocellum celB gene. These similar regions may contain substrate-binding and/or catalytic sites.     

Isolation and sequence analysis of the human corticotropin-releasing factor precursor gene.

A human genomic DNA segment containing the gene for the corticotropin-releasing factor precursor has been isolated by screening a gene library with an ovine cDNA probe. The cloned DNA segment has been subjected to restriction endonuclease mapping and nucleotide sequence analysis. Comparison of the nucleotide sequence of the gene with that of the ovine cDNA indicates that an intron of 800 bp is inserted in the segment encoding the 5'-untranslated region of the mRNA. The segment corresponding to the protein-coding and the 3'-untranslated region of the mRNA is uninterrupted. The mRNA and amino acid sequences of the human corticotropin-releasing factor precursor have been deduced from the corresponding gene sequence. The deduced amino acid sequence of human corticotropin-releasing factor exhibits seven amino acid substitutions in comparison with the ovine counterpart.     

The primary structure of E. coli RNA polymerase, Nucleotide sequence of the rpoC gene and amino acid sequence of the beta''-subunit.

The primary structure of the E. coli rpoC gene (5321 base pairs) coding the beta'-subunit of RNA polymerase as well as its adjacent segment have been determined. The structure analysis of the peptides obtained by cleavage of the protein with cyanogen bromide and trypsin has confirmed the amino acid sequence of the beta'-subunit deduced from the nucleotide sequence analysis. The beta'-subunit of E. coli RNA polymerase contains 1407 amino acid residues. Its translation is initiated by codon GUG and terminated by codon TAA. It has been detected that the sequence following the terminating codon is strikingly homologous to known sequences of rho-independent terminators.     

The nucleotide sequence of the sigma factor gene ntrA (rpoN) of Azotobacter vinelandii: analysis of conserved sequences in NtrA proteins

Summary The nucleotide sequence of the Azotobacter vinelandii ntrA gene has been determined. It encodes a 56916 Dalton acidic polypeptide (AvNtrA) with substantial homology to NtrA from Klebsiella pneumoniae (KpNtrA) and Rhizobium meliloti (RmNtrA). NtrA has been shown to act as a novel RNA polymerase sigma factor but the predicted sequence of AvNtrA substantiates our previous analysis of KpNtrA in showing no substantial homology to other known sigma factors. Alignment of the predicted amino acid sequences of AvNtrA, KpNtrA and RmNtrA identified three regions; two showing>50% homology and an intervening sequence of <10% homology. The predicted protein contains a short sequence near the centre with homology to a conserved region in other sigma factors. The C-terminal region contains a region of homology to the subunit of RNA polymerase (RpoC) and two highly conserved regions one of which is significantly homologous to known DNA-binding motifs. In A. vinelandii, ntrA is followed by another open reading frame (ORF) which is highly homologous to a comparable ORF downstream of ntrA in K. pneumoniae and R. meliloti.     

The Staphylococcus aureus chromosomal gene plaC, identified by mutations amplifying plasmid pT181, encodes a sigma factor.

The Staphylococcus aureus chromosomal gene plaC, identified by mutations such as plaC1 that lead to the amplification of plasmid pT181, has been cloned and sequenced. The plaC gene encodes a protein with high similarity (79% identity) with the vegetative sigma factor of Bacillus subtilis, sigA, suggesting that it acts as an RNA polymerase sigma factor in S.aureus. The plaC1 mutation was found to be a C to T transition leading to a proline to serine substitution at amino acid residue 209 of the protein. In other sigma factors this region of the protein is involved in specific recognition of the -10 promoter sequence. The change in sigma factor activity due to this mutation is characterized by its strict specificity for a limited number of promoters and the rather high amplitude of the effect.     

Cloning and analysis of the gene (rpoDA) for the principal sigma factor of Pseudomonas aeruginosa

A gene (rpoDA) of Pseudomonas aeruginosa whose gene product has a homologous function and structure with the principal sigma factor of Escherichia coli was cloned and sequenced. The DNA region corresponding to one of the two hybridization signals found in P. aeruginosa DNA with a synthetic oligonucleotide probe (rpoD probe) was shown to be able to complement a temperature sensitive mutation of Escherichia coli rpoD gene. The amino acid sequence deduced from the nucleotide sequence of rpoDA showed an extensive homology with that of the principal sigma factor of E. coli throughout the entire region, which indicates that the two gene products have an essentially identical domain structure. A common basic structure observed among principal sigma factors of different eubacterial strains was proposed. RpoDA protein was identified in the extract of the cell carrying a plasmid clone with the rpoDA gene insert by Western blot analysis.