玉米淀粉合酶IIa中的必需精氨酸残基参与ADP-葡萄糖和引物结合。

Essential arginine residues in maize starch synthase IIa are involved in both ADP-glucose and primer binding.

作者信息

Imparl-Radosevich J M, Keeling P L, Guan H

机构信息

ExSeed Genetics, L.L.C., 1568 Food Science Building, Iowa State University, Ames, IA 50011-1061, USA.

出版信息

FEBS Lett. 1999 Sep 3;457(3):357-62. doi: 10.1016/s0014-5793(99)01066-2.

DOI:10.1016/s0014-5793(99)01066-2

PMID:10471808

Abstract

The arginine-specific reagent phenylglyoxal inactivated the activity of maize starch synthase IIa (SSIIa), due to the modification of at least one arginine residue out of a possible 42. The addition of ADPGlc completely protected SSIIa from the inactivation, indicating that arginine may be involved in the interaction of this anionic substrate with SSIIa. However, site-directed mutagenesis of the conserved Arg-214 in SSIIa showed that this amino acid is important for apparent affinity of SSIIa for its primer (amylopectin and glycogen), as evidenced by a marked increase in the K(m) for primer upon substitution of this amino acid with no concomitant change in V(max), K(m) for ADPGlc, or secondary structure. Therefore, Arg-214 of SSIIa appears to play a role in its primer binding.

摘要

精氨酸特异性试剂苯乙二醛使玉米淀粉合酶IIa（SSIIa）的活性失活，这是由于在可能的42个精氨酸残基中至少有一个发生了修饰。添加ADPGlc可完全保护SSIIa不被失活，这表明精氨酸可能参与了这种阴离子底物与SSIIa的相互作用。然而，对SSIIa中保守的Arg-214进行定点诱变表明，该氨基酸对于SSIIa对其引物（支链淀粉和糖原）的表观亲和力很重要，这一点可通过将该氨基酸替换后引物的K(m)显著增加得到证明，而V(max)、ADPGlc的K(m)或二级结构没有伴随变化。因此，SSIIa的Arg-214似乎在其引物结合中发挥作用。