The cartilage matrix protein (CMP) is a major constituent of most cartilages. Published studies have provided some information on its composition, properties and distribution. Isolation and sequencing of the gene for CMP from chick and human sources reveals a high degree of homology, and they both possess extensive sequences which are common to a collagen-binding region of other proteins. Work from Heinegdrd's lab and mine has demonstrated that CMP also binds proteoglycan. So CMP may perform an important structural role through interactions with these two major elements of cartilage extracellular matrix. In the present proposal, studies are designed to confirm and further characterize the interactions of CMP in cartilage. Interactions will be studied using in vitro binding methods, chemical cross-linking and by immunohistological observation. Monoclonal antibodies will, be raised and characterized to facilitate this work. It is known that the amount and insolubility of CMP increases dramatically with age. An additional goal of the present proposal is to establish the basis of this insolubility, and to determine whether CMP, like many other structural molecules of cartilage, becomes increasingly fragmented with age. This study is expected to add to our knowledge of the normal structural organization of cartilage and of major changes which occur with age.