AMEMIYA, Y*; YOUSON, J.H.; Univ. of Toronto at scarborough, Toronto, Canada; Univ. of Toronto at scarborough, Toronto, Canada: DIVERSITY OF THE STANNIOCALCIN MOLECULE

Stanniocalcin (STC) is a homodimeric glycoprotein that was initially recognized as a product of the corpuscles of Stannius (CS) located within the kidneys of the holostean and teleostean fishes. It was later revealed that mammals also contained STC and that its expression is widespread throughout several tissues. Primary structures of fish STC have been determined only in basal and generalized teleosts such as several salmonid species and the Australian eel. Knowledge of the primary structure of STC would help in our understanding of the evolution of this molecule. In the present study, we cloned and compared STC from two holosteans (bowfin and gar), three species of bonytongues, (elephantnose, butterflyfish and arawana), a generalized teleost (white sucker), and a derived teleost (small mouth bass). STCs of the two holosteans, the sucker and the bass consist of eleven cysteine residues like that of most other vertebrates. However, the STCs from the three bonytongues contain only ten cysteine residues because one cysteine is replaced by arginine or histidine. The cysteine substitution occurs at the site of inter-monomeric disulfide linkage. Western blot analysis of arawana CS extract with anti-chum salmon STC revealed a single 21 kDa band under non-reducing conditions, and a single band of 25 kDa under reducing conditions. These data indicate that arawana STC exists as a monomeric peptide but the nature of the STC peptide from the other bonytongues needs to be confirmed. It remains to be determined whether it has any significance for biological activity. (This study was supported by a grant from the Natural Sciences and Engineering Research Council of Canada to JHY)