IngentaConnect Zinc-alpha2-Glycoprotein Has Ribonuclease Activity

Authors: Lei G.^{1, 2}; Arany I.²; Tyring S.K.^{1, 2}; Brysk H.¹; Brysk M.M.^{1, 2, 3}

Source: Archives of Biochemistry and Biophysics, Volume 355, Number 2, July 1998 , pp. 160-164(5)

Abstract:

Zinc-alpha2-glycoprotein (Znalpha2gp) is widely distributed in body fluids and in various epithelia; its gene has been completely sequenced, but its function has long remained elusive. We have found that Znalpha2gp has RNase activity, comparable to onconase but two orders of magnitude less than RNase A. The RNase activity of Znalpha2gp is characterized by maxima in pH at 7.5, in ionic strength at 50 mM NaCl, and in temperature at 60C. It is strongly inhibited by ZnCl2, but unaffected by MgCl2. It is partially inactivated (down to 20) by the placental RNase inhibitor. On synthetic polyribonucleotide substrates, the RNase activity of Znalpha2gp is specific for pyrimidine residues poly(C) and poly(U) equally and cleaves only single-stranded RNA. For onconase, it has been demonstrated that the RNase activity depends on pyroglutamic acid (pyr 1) as the N-terminus; Znalpha2gp also has pyr 1, while RNase A does not. Alignment of the amino acid sequences of Znalpha2gp and onconase or RNase A reveals only modest matches. Despite the more substantial overall structural homology of Znalpha2gp to class I major histocompatibility complex proteins, Znalpha2gp has not been proven to be associated with the immune response and, conversely, we could not detect RNase activity in six class I HLA heavy chains. Copyright 1998 Academic Press.

Language: English

Document Type: Research article

Affiliations: 1: Department of Dermatology 2: Department of Dermatology, Department of Microbiology and Immunology 3: Department of Dermatology, Department of Microbiology and Immunology, Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas, 77555

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