Altering the binuclear manganese cluster of arginase diminishes thermostability and catalytic function.
Scolnick, L.R., Kanyo, Z.F., Cavalli, R.C., Ash, D.E., Christianson, D.W.(1997) Biochemistry 36: 10558-10565
- PubMed: 9265637 
- DOI: https://doi.org/10.1021/bi970800v
- Primary Citation of Related Structures:  
2RLA, 3RLA, 4RLA, 5RLA - PubMed Abstract: 
Arginase is a thermostable (Tm = 75 degrees C) binuclear manganese metalloenzyme which hydrolyzes l-arginine to form l-ornithine and urea. The three-dimensional structures of native metal-depleted arginase, metal-loaded H101N arginase, and metal-depleted H101N arginase have been determined by X-ray crystallographic methods to probe the roles of the manganese ion in site A (Mn2+A) and its ligand H101 in catalysis and thermostability. We correlate these structures with thermal stability and catalytic activity measurements reported here and elsewhere [Cavalli, R. C., Burke, C. J., Kawamoto, S., Soprano, D. R., and Ash, D. E. (1994) Biochemistry 33, 10652-10657]. We conclude that the substitution of a wild-type histidine ligand to Mn2+A compromises metal binding, which in turn compromises protein thermostability and catalytic function. Therefore, a fully occupied binuclear manganese metal cluster is required for optimal catalysis and thermostability.
Organizational Affiliation: 
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323, USA.