The First Virally Encoded Cytochrome P450

Abstract

The genome sequence of the giant virus Acanthamoeba polyphaga mimivirus revealed the presence of two putative cytochrome P450 (CYP) genes. The product of one of the two predicted CYP genes (YP_143162) showed low-level homology to sterol 14-demethylase (CYP51) and contained a C-terminal polypeptide domain of unknown function. YP_143162 expression (without an N-terminal membrane binding domain) in Escherichia coli yields a CYP protein which gives a reduced CO difference maximum at 448 nm and was formally demonstrated as the first viral cytochrome P450. Analysis of binding of lipid and sterol substrates indicated no perturbation in CYP heme environment, and an absence of activity was seen when 14-methyl sterols were used as a substrate. The function of the CYP protein and its C-terminal domain remain unknown. taxidϭ10239&optϭVirus).Acanthamoeba polyphaga mimivirus is the largest known virus, which grows in amoeba (5). In 2004, the 1.2-Mbp genome of mimivirus (GenBank accession no. AY653733) was sequenced (9). Its genome is larger than that of several bacteria and archaea and is predicted to encode 911 proteins, among which only 298 have predicted functions. Many atypical proteins are predicted to be encoded by the mimivirus genome, including key protein translation enzymes, a full complement of DNA repair pathway components, and the unique presence of three different topoisomerases (9). Interestingly, among genes never yet reported to occur in a virus, mimivirus contained two putative gene sequences predicted to encode cytochrome P450 enzymes (GenBank accession no. YP_142886 and YP_143162, also known as MIMI_L532 and MIMI_L808, respectively). First, YP_142886 is a putative protein of 468 amino acids in length. In a BLASTP search, this putative CYP protein showed homology to a range of bacterial P450 proteins, including a P450 protein from Chloroflexus aurantiacus (23% identity) and CYP171 from Streptomyces peucetius (23% identity). Additionally, YP_142886 also showed homology at the same level to nematode P450 proteins, including Caenorhabditis briggsae CYP37B1 (25% identity) and a P450 protein from the sea squirt Ciona intestinalis similar to the CYP4 family (24% identity). Efforts in our laboratory to express the YP_142886 gene and verify that it indeed encodes a cytochrome P450 have been unsuccessful, but additional attempts are in progress. The mimivirus protein YP_143886 was designated CYP5254A1 by David Nelson (http://drnelson.utmem .edu/CytochromeP450.html).The second putative mimivirus CYP protein (YP_143162) showed in a BLASTP search the strongest homology to CYP51 proteins (7) from a variety of organisms, including protozoal CYP51 proteins from, e.g., Leishmania major (23% identity); plant CYP51 proteins from, e.g., Arabidopsis thaliana (22% identity); and fungal CYP51 proteins from, e.g., Aspergillus fumigatus (21% identity). This homology is low, strongly suggesting the absence of a functional link. Further analysis of the YP_143162 709-amino-acid sequence revealed this putative CYP protein to be appro...

Comparative genomic and phylogenetic investigation of the xenobiotic metabolizing arylamine N‐acetyltransferase enzyme family

“…1 and S2), but our search for NAT genes in amoebozoa retrieved only one short EST from Acanthamoeba castellanii (Table S2), bearing limited similarity to the mimivirus NATs. Interestingly, the mimivirus genome has been reported to harbor two putative cytochrome P450 genes [16] which, together with the putative NAT genes identified here, could represent ancient forms of xenobiotic metabolizing enzymes.…”

Unusual Cytochrome P450 Enzymes and Reactions

“…The first viral P450 (CYP5253A1) was discovered in the Mimivirus genome and is fused at its C terminus to a protein of unknown function but containing several post-translational modification sites (phosphorylation, myristoylation, and glycosylation) (98,99). Recent studies showed that the Saccharopolyspora erythraea glycosyltransferase enzyme EryCIII, which produces erythromycin D (from the substrates thiamine diphosphate-D-desosamine and 3-␣-mycarosylerythronolide B), is activated by the addition of the protein EryCII, with which it forms a heterotetrameric (2:2) complex (63).…”

Regioselective Biocatalytic Hydroxylation of Fatty Acids by Cytochrome P450s

“…Cytochrome P450 enzymes (CYPs) are iron (Fe) containing heme-proteins, which are found in most living organisms, including eukaryotes, archaea, bacteria, and viruses [1][2][3][4]. The enzymes catalyze a broad range of reactions such as hydroxylation [5], decarboxylation [6], epoxidation [7], reductive dehalogenation [8], amine/oxygen dealkylation [9], and sulfoxidation [10], employing molecular oxygen and electrons [e.g.…”