Dataset Information

Identification and sequence analysis of two related flagellin genes in Rhizobium meliloti.

ABSTRACT: The genomic region that codes for the flagellin subunits of the complex flagellar filaments of Rhizobium meliloti was cloned and sequenced. Two structural genes, flaA and flaB, that encode 395- and 396-amino-acid polypeptides, respectively, were identified. These exhibit 87% sequence identity. The amino acid sequences of tryptic peptides suggest that both of these subunit proteins are represented in the flagellar filaments. The N-terminal methionine was absent from the mature flagellin subunits. Their derived primary structures show almost no relationship to flagellins from Escherichia coli, Salmonella typhimurium, or Bacillus subtilis but exhibit up to 60% similarity to the N- and C-terminal portions of flagellin from Caulobacter crescentus. It is suggested that the complex flagellar filaments of R. meliloti are unique in being assembled from heterodimers of two related flagellin subunits. The tandemly arranged flagellin genes were shown to be transcribed separately from unusual promoter sequences.

SUBMITTER: Pleier E

PROVIDER: S-EPMC209768 | biostudies-other | 1989 Mar

REPOSITORIES: biostudies-other

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Identification and sequence analysis of two related flagellin genes in Rhizobium meliloti.

Pleier E E Schmitt R R

Journal of bacteriology 19890301 3

The genomic region that codes for the flagellin subunits of the complex flagellar filaments of Rhizobium meliloti was cloned and sequenced. Two structural genes, flaA and flaB, that encode 395- and 396-amino-acid polypeptides, respectively, were identified. These exhibit 87% sequence identity. The amino acid sequences of tryptic peptides suggest that both of these subunit proteins are represented in the flagellar filaments. The N-terminal methionine was absent from the mature flagellin subunits. ...[more]

PMID: 2921241

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Project description:Transposon Tn5-induced C4-dicarboxylate transport mutants of Rhizobium meliloti 2011 which could be complemented by cosmid pRmSC121 were subdivided into two classes. Class I mutants (RMS37 and RMS938) were defective in symbiotic C4-dicarboxylate transport and in nitrogen fixation. They were mutated in the structural gene dctA, which codes for the C4-dicarboxylate carrier. Class II mutants (RMS11, RMS16, RMS17, RMS24, and RMS31) expressed reduced activity in symbiotic C4-dicarboxylate transport and in nitrogen fixation. These mutants were mutated in regulatory dct genes which do not play an essential role in the symbiotic state. Thin sections of alfalfa nodules induced by the wild type and class I and class II mutants were analyzed by light microscopy. Class mutants induced typical Fix- nodules, showing a large senescent zone, whereas nodules induced by class II mutants only differed in an enhanced content of starch granules compared with wild-type nodules. Class I mutants could be complemented by a 2.1-kilobase SalI-HindIII subfragment of cosmid pRmSC121. DNA sequencing of this fragment resulted in the identification of an open reading frame, which was designated dctA because Tn5 insertion sites of the class I mutants mapped within this coding region. The dctA gene was preceded by a nif consensus promoter and an upstream NifA-binding element. Upstream of the dctA promoter, the 5' end of the R. meliloti dctB gene could be localized. The amino acid sequence of the N-terminal part of the R. meliloti DctB protein shared 49% homology with the corresponding part of the R. leguminosarum DctB protein. The DctA protein consisted of 441 or 453 amino acids due to two possible ATG start codons, with calculated molecular masses of 46.1 and 47.6 kilodaltons, respectively. The hydrophobicity plot suggests that DctA is a membrane protein with several membrane passages. The amino acid sequences of the R. meliloti and the R. leguminosarum DctA proteins were highly conserved (82%).

Project description:BACKGROUND: Rhizobium leguminosarum bv. viciae establishes symbiotic nitrogen fixing partnerships with plant species belonging to the Tribe Vicieae, which includes the genera Vicia, Lathyrus, Pisum and Lens. Motility and chemotaxis are important in the ecology of R. leguminosarum to provide a competitive advantage during the early steps of nodulation, but the mechanisms of motility and flagellar assembly remain poorly studied. This paper addresses the role of the seven flagellin genes in producing a functional flagellum. RESULTS: R. leguminosarum strains 3841 and VF39SM have seven flagellin genes (flaA, flaB, flaC, flaD, flaE, flaH, and flaG), which are transcribed separately. The predicted flagellins of 3841 are highly similar or identical to the corresponding flagellins in VF39SM. flaA, flaB, flaC, and flaD are in tandem array and are located in the main flagellar gene cluster. flaH and flaG are located outside of the flagellar/motility region while flaE is plasmid-borne. Five flagellin subunits (FlaA, FlaB, FlaC, FlaE, and FlaG) are highly similar to each other, whereas FlaD and FlaH are more distantly related. All flagellins exhibit conserved amino acid residues at the N- and C-terminal ends and are variable in the central regions. Strain 3841 has 1-3 plain subpolar flagella while strain VF39SM exhibits 4-7 plain peritrichous flagella. Three flagellins (FlaA/B/C) and five flagellins (FlaA/B/C/E/G) were detected by mass spectrometry in the flagellar filaments of strains 3841 and VF39SM, respectively. Mutation of flaA resulted in non-motile VF39SM and extremely reduced motility in 3841. Individual mutations of flaB and flaC resulted in shorter flagellar filaments and consequently reduced swimming and swarming motility for both strains. Mutant VF39SM strains carrying individual mutations in flaD, flaE, flaH, and flaG were not significantly affected in motility and filament morphology. The flagellar filament and the motility of 3841 strains with mutations in flaD and flaG were not significantly affected while flaE and flaH mutants exhibited shortened filaments and reduced swimming motility. CONCLUSION: The results obtained from this study demonstrate that FlaA, FlaB, and FlaC are major components of the flagellar filament while FlaD and FlaG are minor components for R. leguminosarum strains 3841 and VF39SM. We also observed differences between the two strains, wherein FlaE and FlaH appear to be minor components of the flagellar filaments in VF39SM but these flagellin subunits may play more important roles in 3841. This paper also demonstrates that the flagellins of 3841 and VF39SM are possibly glycosylated.

Dataset Information

Identification and sequence analysis of two related flagellin genes in Rhizobium meliloti.

Publications

Identification and sequence analysis of two related flagellin genes in Rhizobium meliloti.

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