Olczak Teresa
Laboratory of Biochemistry, Institute of Biochemistry and Molecular Biology, Wroclaw University, Tamka 2, 50-137 Wroclaw, Poland.
Arch Microbiol. 2006 Nov;186(5):393-402. doi: 10.1007/s00203-006-0151-3. Epub 2006 Jul 28.
The aim of this study was to broaden the current knowledge about the Porphyromonas gingivalis heme receptor HmuR. Site-directed mutagenesis was employed to replace Glu427, Glu448, Glu458 and Glu503 by alanines and to construct a triple Glu427Ala/Glu448Ala/Glu 458Ala mutant. All iron/heme-starved P. gingivalis mutants showed decreased growth recovery when human serum as the iron/heme source was used, hmuR::ermF, hmuR (E503A) and hmuR (E427A,E448A,E458A) mutant strains being the most affected. E. coli cells expressing HmuR with mutated glutamate residues bound hemin, hemoglobin and hemin-serum albumin complex with the same efficiency as did the wild-type recombinant protein, suggesting that the residues were not directly involved in heme binding. These data indicate that in addition to two conserved histidine residues (His95 and His434), NPDL and YRAP motifs, conserved glutamate residues are important for HmuR to utilize heme present in serum hemoproteins.
本研究的目的是拓宽当前关于牙龈卟啉单胞菌血红素受体HmuR的知识。采用定点诱变将谷氨酸427、谷氨酸448、谷氨酸458和谷氨酸503替换为丙氨酸，并构建了三突变体谷氨酸427丙氨酸/谷氨酸448丙氨酸/谷氨酸458丙氨酸。当使用人血清作为铁/血红素来源时，所有铁/血红素饥饿的牙龈卟啉单胞菌突变体生长恢复均降低，其中hmuR::ermF、hmuR（E503A）和hmuR（E427A，E448A，E458A）突变菌株受影响最大。表达谷氨酸残基突变的HmuR的大肠杆菌细胞结合血红素、血红蛋白和血红素 - 血清白蛋白复合物的效率与野生型重组蛋白相同，这表明这些残基不直接参与血红素结合。这些数据表明，除了两个保守的组氨酸残基（His95和His434）、NPDL和YRAP基序外，保守的谷氨酸残基对于HmuR利用血清血红素蛋白中的血红素也很重要。
