» Articles » PMID: 9647803

Molecular Cloning, Sequencing, and Expression of a Chemoreceptor Gene from Leptospirillum Ferrooxidans

Overview
Authors
Affiliations
Soon will be listed here.
Abstract

We have cloned and sequenced a 2,262-bp chromosomal DNA fragment from the chemolithoautotrophic acidophilic bacterium Leptospirillum ferrooxidans. This DNA contained an open reading frame for a 577-amino-acid protein showing several characteristics of the bacterial chemoreceptors and, therefore, we named this gene lcrI for Leptospirillum chemotaxis receptor I. This is the first sequence reported for a gene from L. ferrooxidans encoding a protein. The lcrI gene showed both sigma 28-like and sigma 70-like putative promoters. The LcrI deduced protein contained two hydrophobic regions most likely corresponding to the two transmembrane regions present in all of the methyl-accepting chemotaxis proteins (MCPs) which make them fold with both periplasmic and cytoplasmic domains. We have proposed a cytoplasmic domain for LcrI, which also contains the highly conserved domain (HCD region), present in all of the chemotactic receptors, and two probable methylation sites. The in vitro expression of a DNA plasmid containing the 2,262-bp fragment showed the synthesis of a 58-kDa protein which was immunoprecipitated by antibodies against the Tar protein (an MCP from Escherichia coli), confirming some degree of antigenic conservation. In addition, this 58-kDa protein was expressed in E. coli, being associated with its cytoplasmic membrane fraction. It was not possible to determine a chemotactic receptor function for LcrI expressed in E. coli. This was most likely due to the fact that the periplasmic pH of E. coli, which differs by 3 to 4 pH units from that of acidophilic chemolithotrophs, does not allow the right conformation for the LcrI periplasmic domain.

References
1.
Laemmli U . Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970; 227(5259):680-5. DOI: 10.1038/227680a0. View

2.
Deckers H, Voordouw G . Identification of a large family of genes for putative chemoreceptor proteins in an ordered library of the Desulfovibrio vulgaris Hildenborough genome. J Bacteriol. 1994; 176(2):351-8. PMC: 205057. DOI: 10.1128/jb.176.2.351-358.1994. View

3.
Ohmura N, Tsugita K, Koizumi J, SAIKA H . Sulfur-binding protein of flagella of Thiobacillus ferrooxidans. J Bacteriol. 1996; 178(19):5776-80. PMC: 178419. DOI: 10.1128/jb.178.19.5776-5780.1996. View

4.
Pearson W, Lipman D . Improved tools for biological sequence comparison. Proc Natl Acad Sci U S A. 1988; 85(8):2444-8. PMC: 280013. DOI: 10.1073/pnas.85.8.2444. View

5.
Dolla A, Fu R, Brumlik M, Voordouw G . Nucleotide sequence of dcrA, a Desulfovibrio vulgaris Hildenborough chemoreceptor gene, and its expression in Escherichia coli. J Bacteriol. 1992; 174(6):1726-33. PMC: 205772. DOI: 10.1128/jb.174.6.1726-1733.1992. View