In Escherichia coli at least five enzyme activities required for the beta-oxidation of fatty acids are associated with a multienzyme complex composed of two subunits in alpha 2 beta 2 conformation (A. Pramanik et al., J. Bacteriol. 137:469-473, 1979). In the present work, the DNA sequence of the genes encoding these two subunits, fadB and fadA, has been determined. The direction of transcription was from fadB to fadA rather than from fadA to fadB, as suggested previously (S. K. Spratt et al., J. Bacteriol. 158:535-542, 1984). Only 10 nucleotides separated the coding sequences for the two peptides, confirming the suggestion that these genes form an operon. The peptides encoded by fadB and fadA were 729 amino acids and 387 amino acids, respectively, in length. The larger and smaller peptides had predicted molecular masses of 79,678 and 40,876 Da, respectively. Recently, the sequence of the fadA gene was published in a separate report (Yang et al., J. Biol. Chem. 265:10424-10429, 1990). In this work, most of the DNA sequence for fadA was confirmed, and 10 errors were corrected. Three of these nucleotide changes resulted in five amino acid residue changes predicted in the carboxy terminus of the fadA-encoded peptide. By comparison to other peptide sequences, the alpha subunit encoded within fadB had 31% perfect identity with the rat peroxisomal enoyl-coenzyme A:hydratase-3-hydroxyacyl-coenzyme A dehydrogenase trifunctional enzyme over the entire length of the two peptides. In agreement with the work of Yang et al., the beta subunit encoded within fadA had 35 to 45% perfect identity with five thiolase genes from different eucaryotic sources over the entire length of the peptide.

译文

在大肠杆菌中,脂肪酸的 β-氧化所需的至少五种酶活性与由 α2β2构象中的两个亚基组成的多酶复合物相关 (a.Pramanik等人,J. Bacteriol. 137:469-473,1979)。在本工作中,已经确定了编码这两个亚基fadB和fadA的基因的DNA序列。转录的方向是从fadB到fadA,而不是从fadA到fadB,如前所述 (S. K. Spratt等人,J. Bacteriol. 158:535-542,1984)。只有10个核苷酸分离了两个肽的编码序列,证实了这些基因形成操纵子的暗示。fadB和fadA编码的肽长度分别为729个氨基酸和387个氨基酸。较大和较小的肽分别预测79,678和40,876 Da的分子量。最近,fadA基因的序列发表在单独的报告中 (Yang等人,J. Biol. Chem. 265:10424-10429,1990)。在这项工作中,fadA的大部分DNA序列得到了确认,并纠正了10个错误。这些核苷酸变化中的三个导致fadA编码肽的羧基末端预测的五个氨基酸残基变化。与其他肽序列相比,fadB内编码的 α 亚基与大鼠过氧化物酶体烯酰辅酶a具有31% 完美的同一性: 在两个肽的整个长度上hydratase-3-hydroxyacyl-coenzyme脱氢酶三官能酶。与Yang等人的工作一致,在fadA内编码的 β 亚基在肽的整个长度上与来自不同真核来源的五个硫解酶基因具有35至45% 完美的同一性。

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