The objectives of the proposed research are to confirm, refute or refine the following hypotheses: a) The transport of vitamins across membranes is mediated by specific vitamin-binding glycoproteins. b) The structure of the vitamin-binding protein, not the vitamin, is essential for transport. c) A single transport system recognizes certain structural features such as attached carbohydrate which vitamin-binding proteins have in common. The chicken egg, which is a rich nutritional source of vitamins, will be the experimental system to be examined. Several specific vitamin-binding proteins are known from egg and others would be expected. In particular, proteins which bind pantothenate, thiamine, and vitamin A should be present based on the concentration of these vitamins in egg. The research proposed herein will focus on the isolation and structural characterization of a pantothenate-binding protein which will be compared to other vitamin-binding proteins from chicken egg in an effort to understand the phenomenon of vitamin transport.