helix DNA-binding proteins, including the C-tetminal domain of procaryotic catabolite gene activator protein (CAP), the globular domain of the linker histone HS, and the DNA-binding domain of the hepatocyte nuclear factor-3 (HNF-3). By aligning the helixturn-helix motif of Mbpl with that of CAP and HNF-3, we can suggest the following protein DNA interactions for the Mbpl-DNA complex: major groove contacs with DNA by the recognition helix within the helix-him-helix motif, as well as minor groove contacts by the loop of the ~-hairpin. ~ PS04.05.35 CRYSTALLIZATION OF THE FELINE lJ.vl-MUNODEFICIENCY VIRUS INTEG RASE PROTEIN.