초록 close

A blue protein was purified from the Methylobacillus sp. strain SK1 that is grown on methanol in the pres-ence of copper ion. This protein was found to be a monomer with a molecular weight of 13,500. The Isoelectric point of the protein was estimated to be 8.8. The spectrum of the protein that was treated with fer-ricyanide showed a broad peak around 620 nm, but that of the dithionite-treated protein revealed no peaks. It contained 0.83 mol of EDTA-stable copper per mol protein. Under air, the protein accelerated the inacti-vation of methanol dehydrogenase (MDH). The pro-tein was reducible by phenazine methosulfate or by active MDH that was prepared from cells that were grown in the absence of added copper, but not by methanol, dichlorophenol indophenol, or inactive MDH that was prepared from cells that were grown in the presence of added copper. It was also reducible by active MDH in the presence of methanol. The absorp-tion peak at 340 nm of the active MDH disappeared after the enzyme was treated with ferricyanide, hy-drogen peroxide, or the purified blue protein. The in-active MDH also showed no peak at 340 nm. The 340-nm peak was not recovered after incubation of the inactive MDH and blue protein-treated active MDH with dithionite or methanol. The inactive MDH and blue protein-treated active MDH co-migrated with the active MDH preparation on nondenaturing poly-acrylamide gel, and contained two non-identical sub-units with molecular weights that were identical to those of the active MDH. The N-terminal amino acid sequence of the protein was Ala-Gly-Cys-Ser-Val-Asp-Val-Glu-Ala-Asn-Asp-Ala-Met-Gln-Phe. An analysis of the amino acid composition revealed that the pro-tein contained no tryptophan. It contained three cys-teines per mol protein. The blue protein in Methyloba-cillus sp. strain SK1 was produced only in the cells that were grown in the copper-supplemented medium.