Karkhoff-Schweizer R R, Bruschi M, Voordouw G
Department of Biological Sciences, University of Calgary, Canada.
Eur J Biochem. 1993 Feb 1;211(3):501-7. doi: 10.1111/j.1432-1033.1993.tb17576.x.
It has been shown [Pierik, A. J., Duyvis, M. G., van Helvoort, J. M. L. M., Wolbert, R. B. G. & Hagen, W. R. (1992) Eur. J. Biochem. 205, 111-115] that desulfoviridin, the dissimilatory sulfite reductase of sulfate-reducing bacteria of the genus Desulfovibrio, contains a third, gamma, subunit (11 kDa), in addition to the well-established alpha (50 kDa) and beta (40 kDa) subunits, and an alpha 2 beta 2 gamma 2 subunit structure has been proposed. Cloning and sequencing of the dsvC gene indicated it to encode a protein of 105 amino acids (11.9 kDa; gamma subunit). The finding that the dsvC gene, located on a 3.5-kb SacII fragment, is transcribed in both Escherichia coli and Desulfovibrio vulgaris as an mRNA of only 400-600 nucleotides, and that both the dsvA and dsvB genes are present on a 7.2-kb SacII fragment, indicates that dsvC forms a separate transcriptional unit. The steady-state level of alpha and beta subunits expressed in D. vulgaris Hildenborough cells is rather constant, while that of the gamma subunit increased strongly in the stationary growth phase. Biochemical analysis of the purified protein, expressed in E. coli, and library comparison of its sequence, have so far failed to establish the function of gamma.
已证明[皮埃里克，A. J.，杜维斯，M. G.，范赫尔沃特，J. M. L. M.，沃尔伯特，R. B. G. & 哈根，W. R.（1992年）《欧洲生物化学杂志》205卷，111 - 115页]，脱硫弧菌属硫酸盐还原菌的异化亚硫酸盐还原酶脱硫绿素，除了已确定的α（50 kDa）和β（40 kDa）亚基外，还含有第三个γ亚基（11 kDa），并提出了α2β2γ2亚基结构。dsvC基因的克隆和测序表明它编码一种105个氨基酸的蛋白质（11.9 kDa；γ亚基）。位于3.5 kb SacII片段上的dsvC基因在大肠杆菌和普通脱硫弧菌中均转录为仅400 - 600个核苷酸的mRNA，以及dsvA和dsvB基因均位于7.2 kb SacII片段上这一发现，表明dsvC形成一个单独的转录单元。在普通脱硫弧菌希尔登伯勒菌株细胞中表达的α和β亚基的稳态水平相当恒定，而γ亚基的稳态水平在稳定生长期强烈增加。到目前为止，对在大肠杆菌中表达的纯化蛋白进行的生化分析及其序列的文库比较未能确定γ的功能。
