Unno K, Kishido T, Hosaka M, Okada S
Department of Radiobiochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Yada, Japan.
Biol Pharm Bull. 1997 Dec;20(12):1240-4. doi: 10.1248/bpb.20.1240.
To investigate the role of constitutive hsp70 in protein folding and to probe the supplementation by other hsps in this folding, yeast cells expressing reduced constitutive hsp70 proteins, ssa1ssa2, were transformed with a plasmid expressing a bacterial luciferase protein. With several independent clone cells of transformants, the levels of luciferase activity and some hsps, such as hsp104, hsp90, hsp70 and hsp26, were examined. The luciferase activity was significantly lower in ssa1ssa2 transformants than in the wild type (wt) cell transformed with the same plasmid. Among several clone cells of ssa1ssa2, the cells with higher luciferase activities exhibited higher amounts of Ssa4 which is known to be expressed instead of lacking Ssa1 and Ssa2. The luciferase activity closely correlated with the amount of Ssa proteins, more than with the amount of other hsps. It is suggested that constitutional Ssa "chaperones" are needed for the folding of proteins and, in cells lacking Ssa1 and Ssa2, the increased Ssa4 is thought to partly compensate for their role in the folding of luciferase in vivo.
为了研究组成型热休克蛋白70（hsp70）在蛋白质折叠中的作用，并探究其他热休克蛋白（hsps）在此折叠过程中的补充作用，将表达组成型hsp70蛋白水平降低的酵母细胞ssa1ssa2用表达细菌荧光素酶蛋白的质粒进行转化。对几个独立的转化体克隆细胞，检测了荧光素酶活性水平以及一些热休克蛋白，如hsp104、hsp90、hsp70和hsp26的水平。ssa1ssa2转化体中的荧光素酶活性显著低于用相同质粒转化的野生型（wt）细胞。在ssa1ssa2的几个克隆细胞中，荧光素酶活性较高的细胞表现出较高水平的Ssa4，已知Ssa4会在缺少Ssa1和Ssa2时表达。荧光素酶活性与Ssa蛋白的量密切相关，比与其他热休克蛋白的量更相关。这表明组成型Ssa“伴侣蛋白”对于蛋白质折叠是必需的，并且在缺乏Ssa1和Ssa2的细胞中，增加的Ssa4被认为在体内部分补偿了它们在荧光素酶折叠中的作用。
