HOMOLOGY BETWEEN A HUMAN PROTEIN AND A PROTEIN OF THE GREEN GARDEN PEA

In screening a rat mucosa cDNA subtraction library, a clone that exhib ited a remarkable degree of homology with a previously described cDNA from the green garden pea, designated the 26g pea turgor protein, was found. A partial cDNA sequence from rat and a complete cDNA sequence f rom human were obtained. The deduced human protein had a molecular wei ght of 55,285 and was designated antiquitin because of its remarkable level of conservation through evolution. Human antiquitin was 60% homo logous to the green pea 26g with only a single amino acid gap in each sequence. The 66 amino acids at the carboxyl ends of the human antiqui tin and pea 26g proteins were 86% identical, and one segment of 52 ami no acids was 92% identical. A similar partial sequence encoding 164 am ino acids has been detected in Caenorhabditis elegans. Yeast DNA was f ound to have sequences that hybridize with a human antiquitin probe on Southern blotting. Analysis of the amount of mRNA in various rat and human tissues indicated that the largest amounts were found in rat kid ney and liver and in cultured human hepatoma cells. Only minimal amoun ts were detected in human peripheral blood leukocytes, rat lung, or cu ltured human fibroblasts. Attempts to induce the mRNA by heat-shock, d ehydration, ionizing irradiation, or treatment with iron, t-butylhydro peroxide, or glucocorticoids were unsuccessful. The function of the pr otein remains unknown. (C) 1994 Academic Press, Inc.