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-氧化作用至少需要5种酶活性,这些酶活性与由两个处于α2β2构象的亚基组成的多酶复合物有关(A. Pramanik等人,J。Bacteriol。137:469- 473,1979)。在目前的工作中,已经确定了编码这两个亚基fadB和fadA的基因的DNA序列。如先前所建议的,转录方向是从fadB到fadA,而不是从fadA到fadB(S.K.Spratt等人,J.Bacteriol.158:535-542,1984)。仅10个核苷酸分隔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编码的肽的长度分别为729个氨基酸和387个氨基酸。较大和较小的肽预测分子量分别为79,678和40,876 Da。最近,fadA基因的序列在另一份报告中公开(Yang等人,J.Biol。Chem.265:10424-10429,1990)。在这项工作中,确认了fadA的大多数DNA序列,并纠正了10个错误。这些核苷酸变化中的三个导致在fadA编码肽的羧基末端预测到五个氨基酸残基变化。通过与其他肽序列进行比较,fadB内编码的α亚基与大鼠过氧化物酶体烯酰辅酶A:水合酶-3-羟酰基辅酶A脱氢酶三功能酶具有31%的完全同一性。与Yang等人的工作一致,在fadA中编码的β亚基在整个肽段上与来自不同真核来源的五个硫解酶基因具有35%到45%的完全同一性。

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