The small heat shock proteins from <it>Acidithiobacillus ferrooxidans: </it>gene expression, phylogenetic analysis, and structural modeling

• Main Authors: Ribeiro Daniela A, Del Bem Luiz EV, Vicentini Renato, Ferraz Lúcio FC, Murakami Mario T, Ottoboni Laura MM
• Format: Article
• Language: English
• Published: BMC 2011-12-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/11/259

<p>Abstract</p> <p>Background</p> <p><it>Acidithiobacillus ferrooxidans </it>is an acidophilic, chemolithoautotrophic bacterium that has been successfully used in metal bioleaching. In this study, an analysis of the <it>A. ferrooxidans </it>ATCC 23270 genome revealed the presence of three sHSP genes, Afe_1009, Afe_1437 and Afe_2172, that encode proteins from the HSP20 family, a class of intracellular multimers that is especially important in extremophile microorganisms.</p> <p>Results</p> <p>The expression of the sHSP genes was investigated in <it>A. ferrooxidans </it>cells submitted to a heat shock at 40°C for 15, 30 and 60 minutes. After 60 minutes, the gene on locus Afe_1437 was about 20-fold more highly expressed than the gene on locus Afe_2172. Bioinformatic and phylogenetic analyses showed that the sHSPs from <it>A. ferrooxidans </it>are possible non-paralogous proteins, and are regulated by the σ³²factor, a common transcription factor of heat shock proteins. Structural studies using homology molecular modeling indicated that the proteins encoded by Afe_1009 and Afe_1437 have a conserved α-crystallin domain and share similar structural features with the sHSP from <it>Methanococcus jannaschii</it>, suggesting that their biological assembly involves 24 molecules and resembles a hollow spherical shell.</p> <p>Conclusion</p> <p>We conclude that the sHSPs encoded by the Afe_1437 and Afe_1009 genes are more likely to act as molecular chaperones in the <it>A. ferrooxidans </it>heat shock response. In addition, the three sHSPs from <it>A. ferrooxidans </it>are not recent paralogs, and the Afe_1437 and Afe_1009 genes could be inherited horizontally by <it>A. ferrooxidans</it>.</p>