Karow M L, Rogers E J, Lovett P S, Piggot P J
Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
J Bacteriol. 1998 Aug;180(16):4166-70. doi: 10.1128/JB.180.16.4166-4170.1998.
An unexpectedly high proportion of TGA nonsense mutations was obtained in a collection of chemically induced mutations in the spoIIR locus of Bacillus subtilis. Of 11 different mutations obtained, TGA mutations were found in four codons, whereas only three codons yielded missense mutations. Six suppressors of the TGA mutations were isolated, and five of the suppressing mutations were mapped to the prfB gene encoding protein release factor 2. These are the first mutations shown to map to the B. subtilis prfB locus. The sequence of the prfB gene was completed, and two revisions of the published sequence were made. The five prfB mutations also resulted in suppression of the catA86-TGA mutation to between 19 and 54% of the expression of catA86(+), compared to the readthrough level of 6% in the prfB+ strain. N-terminal sequencing of suppressed catA86-TGA-specified protein demonstrated that the amino acid inserted at UGA because of the prfB1 mutations was tryptophan.
在枯草芽孢杆菌spoIIR基因座的化学诱导突变体库中，获得了比例意外高的TGA无义突变。在获得的11种不同突变中，4个密码子出现了TGA突变，而只有3个密码子产生了错义突变。分离出了6个TGA突变的抑制子，其中5个抑制突变被定位到编码蛋白质释放因子2的prfB基因上。这些是首次显示定位到枯草芽孢杆菌prfB基因座的突变。完成了prfB基因的测序，并对已发表的序列进行了两处修订。与prfB+菌株中6%的通读水平相比，这5个prfB突变还导致catA86-TGA突变的抑制率达到catA86(+)表达水平的19%至54%。对被抑制的catA86-TGA所指定蛋白质的N端测序表明，由于prfB1突变而在UGA处插入的氨基酸是色氨酸。
