PRIMARY STRUCTURE OF THE SOLUBLE LACTOSE BINDING LECTIN L-29 FROM RATAND DOG AND INTERACTION OF ITS NONCOLLAGENOUS PROLINE-RICH, GLYCINE-RICH, TYROSINE-RICH SEQUENCE WITH BACTERIAL AND TISSUE COLLAGENASE

A lactose-binding lectin from rat lung (RL-29) and a related lectin fr om Madin-Darby canine kidney (MDCK) cells have been analyzed with the primary goal of identifying post-translational modifications. The sequ ences show that RL-29 and the dog lectin are homologues of a lectin de signated here as L-29 and elsewhere as CBP-35, epsilonBP, Mac-2, or L- 34. RL-29 has a 140-amino-acid COOH-terminal carbohydrate-binding doma in, a 20-amino-acid NH2-terminal domain, and an intervening domain con sisting of 11 repeating elements rich in Pro, Gly, and Tyr (R-domain). The dog homologue has 14 repeating elements in its R-domain explainin g its larger size. The sensitivity of the R-domain to bacterial collag enase allowed us to isolate the NH2-terminal domain and show that the NH2 terminus was blocked by acetylation and, in the accompanying paper (Huflejt, M. E., Turck, C. W., Lindstedt, R., Barondes, S. H., and Le ffler, H. (1993) J. Biol. Chem. 268, 26712-26718), that the NH2-termin al domain is phosphorylated. In addition, we unexpectedly found an end ogenous component, resembling 92-kDa type IV collagenase, that co-puri fied with L-29 and slowly digested the R-domain. Hence, L-29 is a subs trate for bacterial and tissue collagenases even though the R-domain i s non-collagenous. Moreover, the co-purification suggests a non-enzyma tic interaction between 92-kDa collagenase and L-29.