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

被引:14
作者
Robinson, A
Wu, PSC
Harrop, SJ
Schaeffer, PM
Dosztányi, Z
Gillings, MR
Holmes, AJ
Nevalainen, KMH
Stokes, HW
Otting, G
Dixon, NE
Curmi, PMG
Mabbutt, BC [1 ]
机构
[1] Macquarie Univ, Dept Chem, N Ryde, NSW 2109, Australia
[2] Australian Natl Univ, Res Sch Chem, Canberra, ACT 0200, Australia
[3] Univ New S Wales, Sch Phys, Sydney, NSW 2052, Australia
[4] St Vincents Hosp, Ctr Immunol, Sydney, NSW 2010, Australia
[5] Hungarian Acad Sci, Inst Enzymol, Biol Res Ctr, Budapest, Hungary
[6] Macquarie Univ, Dept Biol Sci, N Ryde, NSW 2109, Australia
基金
澳大利亚研究理事会;
关键词
mobile gene cassette; ORFans; protein prospecting; contaminated soil; ketosteroid isomerase;
D O I
10.1016/j.jmb.2004.12.035
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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 Angstrom resolution. From the three-dimensional structure, Bal32a is found to be a member of the highly adaptable alpha + beta 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. (C) 2004 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1229 / 1241
页数:13
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