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Title: Essential arginine residues in maize starch synthase IIa are involved in both ADP-glucose and primer binding. Author: Imparl-Radosevich JM, Keeling PL, Guan H. Journal: FEBS Lett; 1999 Sep 03; 457(3):357-62. PubMed ID: 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.[Abstract] [Full Text] [Related] [New Search]