Schröder I, Hederstedt L, Kannangara C G, Gough P
Department of Microbiology, University of Lund, Sweden.
Biochem J. 1992 Feb 1;281 ( Pt 3)(Pt 3):843-50. doi: 10.1042/bj2810843.
The Bacillus subtilis hemAXCDBL operon encodes enzymes for the synthesis of 5-aminolaevuline acid via the C5 pathway (hemA and hemL) and uroporphyrinogen III (hemB, hemC and hemD). B. subtilis HemA protein (molecular mass 50 kDa) was overexpressed in hemA mutant of both Escherichia coli and B. subtilis. A mutant B. subtilis HemA protein with a Cys to Tyr change at position 105 was also overexpressed. Both wild-type and mutant HemA proteins migrated as oligomers (molecular mass greater than or equal to 230 kDa) on gel-filtration columns. All column fractions containing wild-type HemA protein had glutamyl-tRNA reductase activity. No glutamyl-tRNA reductase activity was found with the mutant HemA protein. It is concluded that the B. subtilis hemA gene product is identical to, or part of, the glutamyl-tRNA reductase of the C5 pathway.
枯草芽孢杆菌hemAXCDBL操纵子编码通过C5途径合成5-氨基乙酰丙酸的酶（hemA和hemL）以及尿卟啉原III（hemB、hemC和hemD）。枯草芽孢杆菌HemA蛋白（分子量50 kDa）在大肠杆菌和枯草芽孢杆菌的hemA突变体中均过量表达。在第105位发生半胱氨酸到酪氨酸变化的突变型枯草芽孢杆菌HemA蛋白也被过量表达。野生型和突变型HemA蛋白在凝胶过滤柱上均以寡聚体形式迁移（分子量大于或等于230 kDa）。所有含有野生型HemA蛋白的柱级分都具有谷氨酰胺-tRNA还原酶活性。突变型HemA蛋白未发现谷氨酰胺-tRNA还原酶活性。得出的结论是，枯草芽孢杆菌hemA基因产物与C5途径的谷氨酰胺-tRNA还原酶相同或为其一部分。
