MOLECULAR CHARACTERIZATION OF THE HUMAN CARBONIC ANHYDRASE-RELATED PROTEIN (HCA-RP-VIII)

The very evolutionarily conserved human carbonic anhydrase-related pol ypeptide (CA-RP VIII) lacks the carbon-dioxide hydration-activity, cha racteristic of the enzymatically active carbonic anhydrases. We have e xpressed HCA-RP VIII as a glutathione-S-transferase fusion protein (GS T-HCA-RP VIII). The purified HCA-RP VIII showed a substantially higher apparent molecular weight by gel-filtration compared to the molecular weight calculated from the amino acid sequence, indicating a larger t han expected Stoke's radius. Like other studied CA's, the protein unfo lds through two transitions at increasing concentrations of guanidine hydrochloride. The far-UV CD spectra of HCA-RP VIII indicates a second ary structure similar to that of the catalytically active HCA II. The very high sequence identify between human and mouse CA-RP vm (98%), mi ght indicate that the function of the protein involves binding of anot her protein. However, an attempt to use the GST-HCA-RP VIII fusion pro tein to affinity purify a ligand was unsuccessful. (C) 1998 Elsevier S cience B.V. All rights reserved.