Partial amino acid sequence of organ of Corti protein OCP-II.

We have previously described two low-molecular-weight, highly acidic proteins which are present in the organ of Corti in extremely high concentrations. Since the function of these proteins is not known, they have been assigned the tentative names OCP-I and OCP-II. In the hope of obtaining information about their function through homology studies, we have initiated amino acid sequencing of these proteins. We have recently succeeded in obtaining a brief amino-terminal sequence of OCP-II. We now report on a significant extension of the amino-terminal sequence of OCP-II and our first results on sequences of peptide fragments obtained by limited digestion with V8 protease. Together, the sequenced segments account for about one-third of the total sequence. Comparisons with the sequences of known proteins suggest that OCP-II is not a structural protein, but that it may exhibit biologic activity.