Characterization of a CYP153 alkane hydroxylase gene in a Gram-positive Dietzia sp. DQ12-45-1b and its 'team role' with alkW1 in alkane degradation

摘要

CYP153 and AlkB-like hydroxylases were recently discovered in Gram-positive alkane-degrading bacteria. However, it is unclear whether they cooperate with each other in alkane degradation as they do in Gram-negative bacteria. In this paper, we cloned the CYP153 gene from a representative Gram-positive alkane-degrading bacterium, Dietzia sp. DQ12-45-1b. The CYP153 gene transcription in Dietzia sp. DQ12-45-1b and heterologous expression in alkB gene knockout mutant strain Pseudomonas fluorescens KOB2Δ1 both confirmed the functions of CYP153 on C6-C10 n-alkanes degradation, but not on longer chain-length n-alkanes. In addition, substrate-binding analysis of the purified CYP153 protein revealed different substrate affinities to C6-C16 nalkanes, confirming n-alkanes binding to CYP153 protein. Along with AlkW1, an AlkB-like alkane hydroxylase in Dietzia sp. DQ12-45-1b, a teamwork pattern was found in n-alkane degradation, i.e. CYP153 was responsible for hydroxylating n-alkanes shorter than C10 while AlkW1 was responsible for those longer than C14. Further sequence analysis suggested that the high horizontal gene transfer (HGT) potential of CYP153 genes may be universal in Gram-positive alkane-degrading actinomycetes that contain both alkB and CYP153 genes.