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Open Access Research article

Identification and functional analysis of cytochrome P450 complement in Streptomyces virginiae IBL14

Zhi-Zhen Li1, Xiao-Fei Li1, Wei Yang1, Xiang Dong1, Jie Yu2, Shu-Liang Zhu1, Man Li1, Li Xie1 and Wang-Yu Tong1*

Author affiliations

1 Integrated Biotechnology Laboratory, Institute of Health Science, School of Life Science, Anhui University, 111 Jiulong Road, Hefei 230601, China

2 Department of Chemical Engineering, McMaster University, Hamilton, Ontario, L8S 4L7, Canada

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Citation and License

BMC Genomics 2013, 14:130  doi:10.1186/1471-2164-14-130

Published: 27 February 2013

Abstract

Background

As well known, both natural and synthetic steroidal compounds are powerful endocrine disrupting compounds (EDCs) which can cause reproductive toxicity and affect cellular development in mammals and thus are generally regarded as serious contributors to water pollution. Streptomyces virginiae IBL14 is an effective degradative strain for many steroidal compounds and can also catalyze the C25 hydroxylation of diosgenin, the first-ever biotransformation found on the F-ring of diosgenin.

Results

To completely elucidate the hydroxylation function of cytochrome P450 genes (CYPs) found during biotransformation of steroids by S. virginiae IBL14, the whole genome sequencing of this strain was carried out via 454 Sequencing Systems. The analytical results of BLASTP showed that the strain IBL14 contains 33 CYPs, 7 ferredoxins and 3 ferredoxin reductases in its 8.0 Mb linear chromosome. CYPs from S. virginiae IBL14 are phylogenetically closed to those of Streptomyces sp. Mg1 and Streptomyces sp. C. One new subfamily was found as per the fact that the CYP Svu001 in S. virginiae IBL14 shares 66% identity only to that (ZP_05001937, protein identifer) from Streptomyces sp. Mg1. Further analysis showed that among all of the 33 CYPs in S. virginiae IBL14, three CYPs are clustered with ferredoxins, one with ferredoxin and ferredoxin reductase and three CYPs with ATP/GTP binding proteins, four CYPs arranged with transcriptional regulatory genes and one CYP located on the upstream of an ATP-binding protein and transcriptional regulators as well as four CYPs associated with other functional genes involved in secondary metabolism and degradation.

Conclusions

These characteristics found in CYPs from S. virginiae IBL14 show that the EXXR motif in the K-helix is not absolutely conserved in CYP157 family and I-helix not absolutely essential for the CYP structure, too. Experimental results showed that both CYP Svh01 and CYP Svu022 are two hydroxylases, capable of bioconverting diosgenone into isonuatigenone and β-estradiol into estriol, respectively.

Keywords:
Biotransformation; Cytochrome P450; Ferredoxin; Ferredoxin reductase; Gene sequencing; Secondary metabolism