OCP2 exists as a dimer in the organ of Corti

OCP2 is one of the most abundant proteins in the organ of Corti (OC), compr ising approximately 5% of the total protein in the supporting cell populati on. Although the very close homolog, Skp1p, has been implicated in regulati ng cell-cycle progression, the function of OCP2 in the terminally different iated cochlea is presently unknown. We have purified recombinant OCP2 from Escherichia coli and examined the protein by analytical ultracentrifugation . Interestingly, sedimentation equilibrium data collected at 20 degrees C u nequivocally indicate that, at the concentrations present in the OC, free O CP2 would exist as a dimeric species. The apparent sedimentation coefficien t is independent of concentration at loading concentrations between 10 and 100 mu M, indicating the absence of a significant monomer-dimer equilibrium in this concentration range. The functional significance of this Finding i s discussed. (C) 1998 Elsevier Science B.V. All rights reserved.