Ling M, Allen S W, Wood J M
Department of Microbiology, University of Guelph, Ontario, Canada.
J Mol Biol. 1994 Nov 11;243(5):950-6. doi: 10.1006/jmbi.1994.1696.
The PutA protein of Escherichia coli has two enzymatic activities: proline dehydrogenase (PDH) and delta 1-pyrroline-5-carboxylate dehydrogenase (P5CDH). It associates with the cytoplasmic membrane as PDH and P5CDH and with put control region DNA as put repressor. Reduction of the PutA flavin by proline, a PutA conformational change and association of PutA with membranes are coincident. The nucleotide base sequence of E. coli putA was determined, that of S. typhimurium putA was updated and the deduced PutA protein sequences were surveyed for catalytic domains and ligand binding sites. The two sequences were very similar (80.5% and 95% on the nucleic acid and protein levels, respectively). Residues 650 through 1130 of PutA were very similar to the sequences of P5C dehydrogenases and aldehyde dehydrogenases from both prokaryotes and eukaryotes. Glutamate 883 and cysteine 917 of PutA were conserved with the corresponding residues in P5C dehydrogenases and with those proposed to be active site residues in the aldehyde dehydrogenases. Those relationships suggest that gamma-glutamic semialdehyde, believed to equilibrate spontaneously with P5C, is the substrate for P5C dehydrogenases. Residues 340 through 590 of PutA were similar in sequence to proline dehydrogenases from Saccharomyces cerevisiae and Drosophila melanogaster. Limited similarities were also found between residues 315 through 357 of PutA and a consensus sequence near a putative active site and FAD-binding region shared by succinate dehydrogenase sequences from several organisms. Since residues 228 through 358 of PutA were similar in sequence to several serine-pyruvate aminotransferases, PutA is proposed to catalyze the hydrolysis of P5C (a Schiff's base intermediate) to gamma-glutamic semialdehyde. A carboxyl-terminal sequence that resembles a leucine zipper motif may be involved in association of PutA with put control region DNA.
大肠杆菌的PutA蛋白具有两种酶活性：脯氨酸脱氢酶（PDH）和δ1-吡咯啉-5-羧酸脱氢酶（P5CDH）。它作为PDH和P5CDH与细胞质膜结合，并作为Put阻遏物与Put控制区DNA结合。脯氨酸使PutA黄素还原、PutA构象改变以及PutA与膜的结合是同时发生的。测定了大肠杆菌putA的核苷酸碱基序列，更新了鼠伤寒沙门氏菌putA的序列，并对推导的PutA蛋白序列进行了催化结构域和配体结合位点的研究。这两个序列非常相似（核酸水平和蛋白质水平分别为80.5%和95%）。PutA的650至1130位残基与原核生物和真核生物的P5C脱氢酶及醛脱氢酶序列非常相似。PutA的谷氨酸883和半胱氨酸917与P5C脱氢酶中的相应残基以及醛脱氢酶中被认为是活性位点残基的那些残基保守。这些关系表明，被认为能与P5C自发平衡的γ-谷氨半醛是P5C脱氢酶的底物。PutA的340至590位残基在序列上与酿酒酵母和黑腹果蝇的脯氨酸脱氢酶相似。在PutA的315至357位残基与几个生物体的琥珀酸脱氢酶序列所共有的假定活性位点和FAD结合区域附近的共有序列之间也发现了有限的相似性。由于PutA的228至358位残基在序列上与几种丝氨酸-丙酮酸转氨酶相似，因此推测PutA催化P5C（一种席夫碱中间体）水解为γ-谷氨半醛。一个类似于亮氨酸拉链基序的羧基末端序列可能参与PutA与Put控制区DNA的结合。
