CHARACTERIZATION OF A NEW CALCIUM-BINDING PROTEIN ABUNDANT IN AMNIOTIC-FLUID, CAAF2, WHICH IS PRODUCED BY FETAL EPIDERMAL-KERATINOCYTES DURING EMBRYOGENESIS

By using a Ca-45(2+) overlay technique, we found two calcium-binding p roteins (CaBPs) abundant in bovine amniotic fluid, and named them CAAF 1 (calcium-binding protein in amniotic fluid-1) and CAAF2. CAAF1 was i dentified as a novel S100 protein produced by fetal epidermal keratino cytes, squamous epithelial cells and polymorphonuclear leukocytes. Her e, we report the primary structure and the tissue distribution of bovi ne CAAF2. CAAF2 is a newly isolated protein with the two EF hand motif s peculiar to S100 proteins, and 29.7% homology to CAAF1. CAAF2 is 63. 4% homologous to human psoriasin, a S100 protein upregulated in psoria tic epidermis. Northern blot analysis demonstrates that CAAF2 is uniqu e in that it is exclusively expressed in the epidermis. Our results su ggest that the majority of CaBPs in amniotic fluid consist of two dist inct S100 proteins, CAAF1 and CAAF2, which are produced by fetal epide rmal keratinocytes. (C) 1996 Academic Press, Inc.