Monkey Clara cell 10 kDa protein (CC10): a characterization of the amino acid sequence with an evolutional comparison...

Monkey Clara cell 10 kDa protein (CC10) was purified from monkey lung lavage. This protein showed an apparent molecular weight of about 10 kDa and 5 kDa under non-reducing and reducing conditions, respectively, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. From the amino acid sequence data, monkey CC10 protein consisted of two identical 70-amino-acid polypeptide chains joined by two cystine residues, and possessed sequence identities of 78.6%, 52.9%, 52.9%, and 44.3% with human CC10, rat CC10 (PCB binding protein), rabbit uteroglobin, and mouse CC10, respectively. When monkey CC10 was compared with rabbit uteroglobin (progesterone binding protein), two polar residues of Tyr-21 and Thr-60, important for progesterone binding specificity, were substituted for Phe-21 and Met-60, and thus monkey CC10 may not have a binding capacity with progesterone. Monkey CC10 also possessed a surface homology with lipocortin I (anti-inflammatory peptide), thus suggesting that monkey CC10 plays a role in the anti-inflammatory process at the air-liquid interface over the bronchio-bronchiolar epithelium.