This project focuses on the sequence analysis, structure-function relationships, and post-translational modifications of proteins. By an improved method for purification of the anti-HIV protein MAP 30 from Momordica charantia seeds, an additional component designated as MAP 30II was isolated and found to have ribosome-inactivating activity and topoisomerase-like activity, and to inhibit HIV-1 infection as well as replication. Neither cytotoxicity to the host cells nor toxicity in mice were detected. MAP 30II consists of 252 or 253 amino acid residues in a single chain without intra-chain disulfide linkages. It has Asp as N- terminus and Gly or Asp as C-terminus, and is homologous in sequence with the abortifacient, alpha-trichosanthin. The primary amino acid sequence and the phosphorylation site of a heat- and acid-labile protein kinase substrate from rat brain were also determined. The amino acid sequence was identical to the 78-residue sequence deduced from rat brain RC3 cDNA and is homologous to bovine neurogranin. Analyses of 32P-labeled tryptic and BrCN cleaved peptides showed that only one residue (Ser36) was phosphorylated. The sequence can be divided into three segments with the following features: (1) a highly acidic region at residues 1-25; (2) the PKC phosphorylation site and calmodulin- binding domain in the middle; and (3) a collagen chain-like structure in the last 25 residues. Based on these features, a specific PKC substrate peptide (AAAKIQASFRGHMARKKIK-amide) was designed for assay of PKC levels in tissues and cells.
