Integron-associated mobile gene cassettes code for folded proteins: the structure of Bal32a, a new member of the adaptable α+β barrel family.

Robinson, Andrew, Wu, Peter S.-C., Harrop, Stephen J. , Schaeffer, Patrick M. , Dosztanyi, Zsuzsanna, Gillings, Michael R., Holmes, Andrew J. , Nevalainen, K. M. Helena, Stokes, H. W., Otting, Gottfried, Dixon, Nicholas E., Curmi, Paul M. G., and Mabbutt, Bridget C. (2005) Integron-associated mobile gene cassettes code for folded proteins: the structure of Bal32a, a new member of the adaptable α+β barrel family. Journal of Molecular Biology, 346 (5). pp. 1229-1241.

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Abstract

The wide-ranging physiology and large genetic variability observed for prokaryotes is largely attributed, not to the prokaryotic genome itself, but rather to mechanisms of lateral gene transfer. Cassette PCR has been used to sample the integron/gene cassette metagenome from different natural environments without laboratory cultivation of the host organism, and without prior knowledge of any target protein sequence. Since over 90% of cassette genes are unrelated to any sequence in the current databases, it is not clear whether these genes code for folded functional proteins. We have selected a sample of eight cassette-encoded genes with no known homologs; five have been isolated as soluble protein products and shown by biophysical techniques to be folded. In solution, at least three of these proteins organise as stable oligomeric assemblies. The tertiary structure of one of these, Bal32a derived from a contaminated soil site, has been solved by X-ray crystallography to 1.8 Å resolution. From the three-dimensional structure, Bal32a is found to be a member of the highly adaptable α+β barrel family of transport proteins and enzymes. In Bal32a, the barrel cavity is unusually deep and inaccessible to solvent. Polar side-chains in its interior are reminiscent of catalytic sites of limonene-1,2-epoxide hydrolase and nogalonic acid methyl ester cyclase. These studies demonstrate the viability of direct sampling of mobile DNA as a route for the discovery of novel proteins.

Item ID: 14908
Item Type: Article (Refereed Research - C1)
Keywords: mobile gene cassette; ORFans; protein prospecting; contaminated soil; ketosteroid isomerase
ISSN: 0022-2836
Date Deposited: 08 Nov 2010 04:56
FoR Codes: 06 BIOLOGICAL SCIENCES > 0604 Genetics > 060408 Genomics @ 50%
06 BIOLOGICAL SCIENCES > 0601 Biochemistry and Cell Biology > 060109 Proteomics and Intermolecular Interactions (excl Medical Proteomics) @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
Citation Count from Web of Science Web of Science 12
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