Chistoserdova L V, Lidstrom M E
W.M. Keck Laboratories 138-78, California Institute of Technology, Pasadena 91125.
J Bacteriol. 1994 Nov;176(21):6759-62. doi: 10.1128/jb.176.21.6759-6762.1994.
The gene (glyA) of Methylobacterium extorquens AM1 encoding serine hydroxymethyltransferase (SHMT), one of the key enzymes of the serine cycle for C1 assimilation, was isolated by using a synthetic oligonucleotide with a sequence based on amino acid sequence conserved in SHMTs from different sources. The amino acid sequence deduced from the gene revealed high similarity to those of known SHMTs. The cloned gene was inactivated by insertion of a kanamycin resistance gene, and recombination of this insertion derivative with the wild-type gene produced an SHMT null mutant. Surprisingly, this mutant had lost its ability to grow on C1 as well as on C2 compounds but was still able to grow on succinate. The DNA fragment containing glyA was shown not to be linked with fragments carrying serine cycle genes identified earlier, making it the fourth chromosomal region of M. extorquens AM1 to be indicated as being involved in C1 assimilation.
利用基于不同来源丝氨酸羟甲基转移酶（SHMT）中保守氨基酸序列设计的合成寡核苷酸，分离出了嗜甲基菌AM1编码丝氨酸羟甲基转移酶（SHMT）的基因（glyA），SHMT是C1同化丝氨酸循环的关键酶之一。从该基因推导的氨基酸序列与已知SHMT的氨基酸序列高度相似。通过插入卡那霉素抗性基因使克隆基因失活，该插入衍生物与野生型基因重组产生了一个SHMT缺失突变体。令人惊讶的是，该突变体失去了在C1以及C2化合物上生长的能力，但仍能在琥珀酸上生长。含有glyA的DNA片段被证明与先前鉴定的携带丝氨酸循环基因的片段不相连，这使其成为嗜甲基菌AM1中被表明参与C1同化的第四个染色体区域。
