1urd: Difference between revisions

Maltose-binding proteins act as primary receptors in bacterial transport, and chemotaxis systems. We report here crystal structures of the, thermoacidostable maltose-binding protein from Alicyclobacillus, acidocaldarius, and explore its modes of binding to maltose and, maltotriose. Further, comparison with the structures of related proteins, from Escherichia coli (a mesophile), and two hyperthermophiles (Pyrococcus, furiosus and Thermococcus litoralis) allows an investigation of the basis, of thermo- and acidostability in this family of proteins.The, thermoacidophilic protein has fewer charged residues than the other three, structures, which is compensated by an increase in the number of polar, residues. Although the content of acidic and basic residues is, approximately equal, more basic residues are exposed on its surface, whereas most acidic residues are buried in the interior. As a consequence, this protein has a highly positive surface charge. Fewer salt bridges are, buried than in the other MBP structures, but the number exposed on its, surface does not appear to be unusual. These features appear to be, correlated with the acidostability of the A. acidocaldarius protein rather, than its thermostability.An analysis of cavities within the proteins shows, that the extremophile proteins are more closely packed than the mesophilic, one. Proline content is slightly higher in the hyperthermophiles and, thermoacidophiles than in mesophiles, and this amino acid is more common, at the second position of beta-turns, properties that are also probably, related to thermostability. Secondary structural content does not vary, greatly in the different structures, and so is not a contributing factor.

1URD is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Alicyclobacillus_acidocaldarius Alicyclobacillus acidocaldarius] with MLR as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1URD OCA].  

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