Fig. 6.

Proposed model of substrate binding and product release. Schematic representation of the conformational changes associated with substrate binding and product release. Step 1: prior to encounter with a Dol-P acceptor molecule. GDP-Man and metal ion are bound in the active site. Step 2: Dol-P binding, IFH2 movement, opening of “back door” and of the acceptor loop. Step 3: glycosyl transfer followed and subsequent release of GDP and metal ion. Step 4: binding of GDP-Man and metal ion, release of Dol-P-Man, closure of back door and acceptor loop. See text for further details. Color scheme: Catalytic domain, blue; IFH2, green; TM domain, red; acceptor loop, pink; GDP-Man, orange and yellow ovals; metal ion, purple circle; Phe177, gray oval; Dol-P isoprenoid chain, gray; and Dol-P phosphate group, green circle