Impact of intra-subunit interactions on the dimeric arginine kinase activity and structural stability

Arginine kinase (AK) catalyzes the reversible phosphorylation of arginine by ATP, yielding the phosphoarginine. In this research, six conserved residues located on the intra-subunit domain-domain interfaces were mutated to explore their roles in the activity and structural stability of dimer AK. The mutations D69A, E70A, E71A and F80A led to pronounced loss of AK activity and structural stability. Although the mutations V75A and F76A had little effect on AK activity and structure, they caused gradually decreased the stability and reactivation of dimer AK. Our results suggested that the mutations might affect the correct positioning of the N-loop and C-loop thus disrupted the efficient recognition and interactions between the N-terminal domain and C-terminal domain which may influence the compact dimer structure, and result in decreased activity and structural stability. (C) 2011 Elsevier B.V. All rights reserved.