Primary structure of the thermostable formyltetrahydrofolate synthetase from Clostridium thermoaceticum.
Primary structure of the thermostable formyltetrahydrofolate synthetase from Clostridium thermoaceticum.
复制标题
来自热乙酸梭菌的热稳定性甲酰四氢叶酸合成酶的一级结构。
DOI：
10.1021/bi00476a007
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Ljungdahl,LG
中科院分区：
文献类型：
--
作者：
Lovell,CR;Przybyla,A;Ljungdahl,LG
Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, and Department of Biochemistry and Center for Biological Resource Recovery, University of Georgia, Athens, Georgia 30602 Received December 28, 1989; Revised Manuscript Received March 29, 1990 abstract: The complete nucleotide sequence of the Clostridium thermoaceticum formyltetrahydrofolate synthetase (FTHFS) was determined and the primary structure of the protein predicted. The gene was 1680 nucleotides long, encoding a protein of 559 amino acid residues with a calculated subunit molecular weight of 59983. The initiation codon was UUG, with a probable ribosome binding site 11 bases upstream. A putative ATP bindingdomain was identified. Two Cys residues likely to be involved in subunit aggregation were tentatively identified. No characterization of the tetrahydrofolate (THF) binding domain was possible on the basis of the sequence. A high level of amino acid sequence conservation between the C. thermoaceticum FTHFS and the published sequences of C. acidiurici FTHFS and the FTHFS domains of the Saccharomyces cerevisiae CpTHF synthases was found. Of the 556 residues shared between the two clostridial sequences, 66.4% are identical. If conservative substitutions are allowed, this percentage rises to 75%. Over 47% of the residues shared between the C. thermoaceticum FTHFS and the yeast Q-THF synthases are identical, 57.4% if conservative substitutions are allowed. Hydrophobicity profiles of the C. acidiurici and C. thermoaceticum enzymes were very similar and did not support the idea that large hydrophobic domains play an important role in thermostabilizing the C. thermoaceticum FTHFS. e activation of formate by 10-formyltetrahydrofolate synthetase (EC 6.3. 4.3) is a key reaction in acetogenic and purinolytic bacteria. Acetogens synthesize acetyl-CoA via the Wood pathway of autotrophic C02 fixation, which uses this enzyme to activate formate in the presence of tetrahydrofolate and ATP (Wood et al., 1986; Fuchs, 1986; Ljungdahl, 1986). Purine fermenters synthesize acetate via the glycine syn-thase/glycine reductase pathway, which also utilizes FTHFS1 in a C02 fixation process (Waber & Wood, 1979; Schiefer-Ullrich et al., 1984; Ljundahl, 1984). FTHFS is present in both acetogenic and purinolytic bacteria at high levels. Many of the physical, chemical, and catalytic properties of FTHFSs purified from acetogenicand purinolytic Clostridia are very similar. FTHFS has been purified to homogeneity from two acetogens, the thermophile Clostridium thermoaceticum (Ljungdahl et al., 1970) and the mesophile C. for-micoaceticum (O’Brien et al., 1976), and from two mesophilic purine fermenters, C. acidiurici and C. cylindrosporum (Rabinowitz & Pricer, 1962). Each of these enzymes consists of foursubunits of Mr= 60000 that are identical within the enzyme from each source (MacKenzie & Rabinowitz, 1971). The substrate turnover rates, activation energies, and halfsaturation constants of these enzymes are very similar, as are their amino acid compositions (O’Brien et al., 1976). The subunits of synthetases from C. thermoaceticum and C cy-lindrosporum have been observed to form dimers, which in turn yield the tetrameric enzyme (Mayer et al., 1982). The f This research was supported by NIH Biomedical Research Support Grant Award S07 RR07160, the Carolina Venture Fund, and the National Institute of Diabetesand Digestive and Kidney Diseases, Grant DK 27323. A preliminary account of this work was part of a presentation given at the annual meeting of the American Society forMicrobiology, New Orleans, LA, 1989 …
