Structure and function of low-molecular-weight proteins with a cytochrome P450 heme-binding domain derived from the basidiomycete Lentinus edodes

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A novel gene shp1 isolated from the basidiomycete Lentinus edodes DDLE1 encodes a low-molecular-weight protein with a cytochrome P450 heme-binding domain. The 5' untranslated region of shp1 contained a repeat sequence (named LESR1) highly interspersed over L. edodes genome, which is transcribed together with the coding region as a single transcript. The SHP1 protein consisted of 74 amino acids residues and contained the region highly homologous to the heme-binding regions of L. edodes P450s (500 amino acids) isolated from FMC2 strain in this study. The shp1 isolated from L. edodes FMC2 was found to encode 115 amino acids. The DDLE1 SHP1 protein produced in E. coli was mixed with protoheme in the presence of deoxycholic acid, followed by the treatment of reconstitution of the protein-protoheme complex. Carbon monooxide difference spectrum of the mixture suggests that the SHP1 is a heme-binding protein with a similarity to P450s in the type of heme binding. Then we attempted to determine the substrate and reaction product of SHP1 by using S. cerevisiae system used for the detection of Aflatoxin B1 generating activity of the ascomycetous fungal P450s. Unfortunately the substrate for SHP1 hasn't been determined until now.