Ronda C, García J L, García E, Sánchez-Puelles J M, López R
Eur J Biochem. 1987 May 4;164(3):621-4. doi: 10.1111/j.1432-1033.1987.tb11172.x.
A pneumococcal recombinant plasmid, pRG2, containing the lytA gene that codes for the pneumococcal N-acetylmuramoyl-L-alanine amidase has been constructed using the pneumococcal plasmid pLS1 as a vector. pRG2 was introduced by genetic transformation into a mutant of Streptococcus pneumoniae (M31) that has a complete deletion of the lytA gene. The transformed strain (M51) grew at a normal growth rate as 'diplo' cells and underwent autolysis at the end of the exponential phase of growth, two properties that had been lost in the deleted mutant M31. M51 lysed very rapidly at the end of the exponential phase when the cells were grown in choline-containing medium probably because of the higher level of amidase activity present in this strain as compared to the lysis-prone strain M11. These findings show that the expression of the plasmid-linked gene was placed under the mechanism(s) of control of the cell during the exponential phase. Our results demonstrate that the physiological role of the pneumococcal amidase was to catalyze the separation of the daughter cells at the end of the cell division to produce diplo cells; in addition we have also confirmed the basic role of this autolysin in the bacteriolytic nature of beta-lactam antibiotics.
一种含有编码肺炎球菌N - 乙酰胞壁酰 - L - 丙氨酸酰胺酶的lytA基因的肺炎球菌重组质粒pRG2，已以肺炎球菌质粒pLS1为载体构建而成。通过基因转化将pRG2导入肺炎链球菌（M31）的一个突变体，该突变体的lytA基因完全缺失。转化后的菌株（M51）以正常生长速率生长为“双球菌”细胞，并在生长指数期结束时发生自溶，这是缺失突变体M31所丧失的两个特性。当细胞在含胆碱的培养基中生长时，M51在指数期结束时非常迅速地裂解，这可能是因为与易裂解菌株M11相比，该菌株中存在更高水平的酰胺酶活性。这些发现表明，质粒连接基因的表达在指数期受到细胞控制机制的调控。我们的结果表明，肺炎球菌酰胺酶的生理作用是在细胞分裂结束时催化子细胞分离以产生双球菌细胞；此外，我们还证实了这种自溶素在β - 内酰胺抗生素的溶菌性质中的基本作用。
