三维结构的adenosylcobinamide磷酸激酶/ adenosylcobinamide guanylyltransferase (CobU)与GMP:证据substrate-induced转移酶活性部位。
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汤普森结核病,托马斯毫克,Escalante-Semerena JC, Rayment我
三维结构的adenosylcobinamide磷酸激酶/ adenosylcobinamide guanylyltransferase (CobU)与GMP:证据substrate-induced转移酶活性部位。
生物化学。1999年10月5日,38 (40):12995 - 3005。
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10529169 (在PubMed]
- 文摘
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adenosylcobinamide x射线晶体结构的磷酸激酶/ adenosylcobinamide guanylyltransferase (CobU)鼠伤寒沙门氏菌绑定到GMP一直由分子置换2.2决议。CobU是一种双功能酶,它催化的磷酸化1-amino-O-2-propanol adenosylcobinamide环侧链和随后的功能作为guanylyltransferase adenosylcobinamide.GDP形式。转移酶活动包括共价enzyme-guanylyl中间,最有可能phosphoramidate联系他(46)。之前的研究表明,这种酶是homotrimer采用一个纸风车形状。每个单元由六个平行beta-strands和单个域的一个反平行的链在两侧,共有五个阿尔法螺旋和一个螺旋。有趣的是,他在酶蛋白(46)位于相当距离激酶活性部位或P-loop图案和solvent-exposed(汤普森,t . B。et al。(1998)生物化学37岁,7686 - 7695]。检查两个活动网站的结构关系,CobU共晶三磷酸鸟苷和焦磷酸。水晶属于空间群P2(1) 2(1) 2(1)与以下单位细胞维度:a = 58岁。4 A、b = 87.8 A和c = 101.6。结构显示了水解产物GMP电子密度,而不是预期的共价guanylyl中间似乎是水解的晶格。 Even so, CobU exhibits a substantial conformational rearrangement. The helix axis containing His(46), the site of guanylylation, rotates 30 degrees and translates 11 A relative to the apo structure and is accompanied by compensatory unwinding and rewinding at the helix ends to allow the induction of a guanosine binding pocket between beta-strand 2 and alpha-helix 2. This conformational change brings the C(alpha) of His(46) approximately 10 A closer to the P-loop motif such that a phosphate ion located in the P-loop is only 6 A from the alpha-phosphate of GMP. This suggests that the P-loop motif may be used to coordinate the terminal phosphates in both the transferase and kinase reactions and implies that the active sites for both reactions overlap.