Biosynthesis of intestinal microvillar proteins. Rapid expression of cytoskeletal components in microvilli of pig small intestinal mucosal explants.

Using alkaline extraction to separate cytoskeletal and membrane proteins of intestinal microvilli, the kinetics of assembly of these two microvillar protein compartments was studied by pulse-chase labelling of pig small intestinal mucosal explants, kept in organ culture. Following a 10 min pulse of [35S]methionine, the membrane proteins did not appear in the microvillar fraction until after 40-60 min of chase. In contrast, the cytoskeletal components, of which the 110-kDa protein and villin were immunologically identified, were expressed in the microvillar fraction immediately after the 10 min pulse. These different kinetics of appearance indicate that the two microvillar protein compartments have separate mechanisms of biosynthesis and microvillar expression.