Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634-0318, USA.
Archaea. 2012;2012:509579. doi: 10.1155/2012/509579. Epub 2012 Aug 15.
The acyl-adenylate-forming enzyme superfamily, consisting of acyl- and aryl-CoA synthetases, the adenylation domain of the nonribosomal peptide synthetases, and luciferase, has three signature motifs (I-III) and ten conserved core motifs (A1-A10), some of which overlap the signature motifs. The consensus sequence for signature motif III (core motif A7) in acetyl-CoA synthetase is Y-X-S/T/A-G-D, with an invariant fifth position, highly conserved first and fourth positions, and variable second and third positions. Kinetic studies of enzyme variants revealed that an alteration at any position resulted in a strong decrease in the catalytic rate, although the most deleterious effects were observed when the first or fifth positions were changed. Structural modeling suggests that the highly conserved Tyr in the first position plays a key role in active site architecture through interaction with a highly conserved active-site Gln, and the invariant Asp in the fifth position plays a critical role in ATP binding and catalysis through interaction with the 2'- and 3'-OH groups of the ribose moiety. Interactions between these Asp and ATP are observed in all structures available for members of the superfamily, consistent with a critical role in substrate binding and catalysis for this invariant residue.
酰基辅酶 A 形成酶超家族由酰基辅酶 A 和芳基 CoA 合成酶、非核糖体肽合成酶的腺苷酸化结构域和荧光素酶组成，具有三个特征基序（I-III）和十个保守核心基序（A1-A10），其中一些与特征基序重叠。乙酰辅酶 A 合成酶中特征基序 III（核心基序 A7）的保守序列为 Y-X-S/T/A-G-D，第五位不变，第一和第四位高度保守，第二和第三位可变。对酶变体的动力学研究表明，任何位置的改变都会导致催化速率大幅下降，尽管当第一或第五位发生改变时，会观察到最具破坏性的影响。结构建模表明，第一个位置高度保守的 Tyr 通过与高度保守的活性位点 Gln 相互作用，在活性位点结构中发挥关键作用，而第五位不变的 Asp 通过与核糖部分的 2'-和 3'-OH 基团相互作用，在 ATP 结合和催化中发挥关键作用。在可获得的超家族成员的所有结构中都观察到这些 Asp 与 ATP 之间的相互作用，这与该不变残基在底物结合和催化中的关键作用一致。
