The lytB Gene of Escherichia coli Is Essential and Specifies a Product Needed for Isoprenoid Biosynthesis

LytB and GcpE, because they are codistributed with other pathway enzymes, have been predicted to catalyze unknown steps in the nonmevalonate pathway for isoprenoid biosynthesis. We constructed a conditional Escherichia coli lytB mutant and found that LytB is essential for survival and that depletion of LytB results in cell lysis, which is consistent with a role for this protein in isoprenoid biosynthesis. Alcohols which can be converted to pathway intermediates beyond the hypothesized LytB step(s) support limited growth of E. coli lytB mutants. An informatic analysis of protein structure suggested that GcpE is a globular protein of the TIM barrel class and that LytB is also a globular protein. Possible biochemical roles for LytB and GcpE are suggested.

鉴于LytB与GcpE可与其他途径酶协同分布，研究人员推测二者能够催化异戊二烯生物合成非甲羟戊酸途径中尚未阐明的反应步骤。本研究构建了条件型大肠杆菌（Escherichia coli）lytB突变株，实验结果显示LytB是细菌存活必需的蛋白，且LytB耗竭会引发细胞裂解，这与该蛋白参与异戊二烯生物合成的功能推测一致。可转化为LytB假说催化步骤下游途径中间体的醇类化合物，能够部分维持大肠杆菌lytB突变株的有限生长。蛋白质结构生物信息学分析表明，GcpE属于TIM桶（TIM barrel）折叠家族的球状蛋白，LytB同样为球状蛋白。本研究还对LytB与GcpE潜在的生化功能进行了推测。