Cirillo J D, Weisbrod T R, Pascopella L, Bloom B R, Jacobs W R
Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461.
Mol Microbiol. 1994 Feb;11(4):629-39. doi: 10.1111/j.1365-2958.1994.tb00342.x.
Diaminopimelic acid (DAP) is a major component of the peptidoglycan layer of the mycobacterial cell wall. The mycobacterial cell wall has been implicated as a potential virulence factor and is highly immunogenic. The pathway for biosynthesis of DAP may serve as a target in the design of antimycobacterial agents and construction of in vivo selection systems. Despite its significance, this biosynthetic pathway is poorly understood in mycobacteria. In order to develop a better understanding of mycobacterial DAP biosynthesis, the aspartate semialdehyde dehydrogenase (asd) genes of Mycobacterium smegmatis, bacille Calmette-Guerin (BCG), Mycobacterium avium, Mycobacterium leprae, and Mycobacterium tuberculosis were isolated. The M. smegmatis asd gene was isolated by complementation in Escherichia coli. This gene was then used to isolate the asd genes from other mycobacteria. The asd-complementing fragments from BCG and M. smegmatis were sequenced. An open reading frame upstream of the mycobacterial asd gene was identified as the mycobacterial aspartokinase gene (ask). Primer extension analysis revealed that the only transcriptional start in this region is found 5' of the ask gene. This observation indicates that the mycobacterial ask and asd genes are in an operon.
二氨基庚二酸（DAP）是分枝杆菌细胞壁肽聚糖层的主要成分。分枝杆菌细胞壁被认为是一种潜在的毒力因子，且具有高度免疫原性。DAP的生物合成途径可能成为抗分枝杆菌药物设计和体内选择系统构建的靶点。尽管其具有重要意义，但分枝杆菌中该生物合成途径仍未被充分了解。为了更好地理解分枝杆菌DAP的生物合成，我们分离了耻垢分枝杆菌、卡介苗（BCG）、鸟分枝杆菌、麻风分枝杆菌和结核分枝杆菌的天冬氨酸半醛脱氢酶（asd）基因。耻垢分枝杆菌的asd基因通过在大肠杆菌中的互补作用得以分离。然后利用该基因从其他分枝杆菌中分离asd基因。对卡介苗和耻垢分枝杆菌的asd互补片段进行了测序。在分枝杆菌asd基因上游的一个开放阅读框被鉴定为分枝杆菌天冬氨酸激酶基因（ask）。引物延伸分析表明，该区域唯一的转录起始位点位于ask基因的5'端。这一观察结果表明，分枝杆菌的ask和asd基因存在于一个操纵子中。
