Structure and putative function of a murine epididymal retinoic acid-binding protein (mE-RABP).

J. J. Lareyre, Vanderbilt University
M. G. Mattéi, Vanderbilt University
S. Kasper, Vanderbilt University
M. E. Newcomer, Vanderbilt University
D. E. Ong, Vanderbilt University
R. J. Matusik, Vanderbilt University
M. C. Orgebin-Crist, Vanderbilt University

Abstract

Vitamin A is required to maintain the epididymal epithelium. In this report, the characterization and putative functions of a murine epididymal retinoic acid-binding protein (mE-RABP) that is secreted into the lumen from the mid-/distal caput epididymidis are discussed. The amino acid sequence analysis of the mE-RABP preprotein shows that mE-RABP is the mouse orthologue of the rat epididymal secretory protein I (ESPI). These proteins belong to the lipocalin superfamily and bind to active retinoids but not to retinol. Therefore, we propose that mE-RABP may function as an extracellular retinoid carrier-protein involved in the paracrine regulation of epididymal function by retinoids.