A convenient and versatile approach to the direct synthesis of a peptide-antigen matrix by the solid-phase method is described. The approach is called the multiple antigen peptide system (MAP) and it utilizes a simple scaffolding of a low number of sequential levels (n) of a trifunctional amino acid as the core matrix and 2n peptide antigens to form a macromolecule with a high density of peptide antigens of final Mr 10,000. The MAP model chosen for study was an octa-branching MAP consisting of a core matrix made up of three levels of lysine and eight amino terminals for anchoring peptide antigens. The MAP, containing both the core matrix and peptides of 9-16 amino acids, was prepared in a single synthesis by the solid-phase method. Six different MAPs elicited specific antibodies in rabbits and mice, of which five produced antibodies that reacted with their corresponding native proteins. In rabbits, the sera had a considerably higher titer of antibodies than sera prepared from the same peptides anchored covalently to keyhole limpet hemocyanin as carrier. Thus, the MAP provided a general, but chemically unambiguous, approach for the preparation of carrier-bound antigens of predetermined and reproducible structure and might be suitable for generating vaccines.

Proteases are ubiquitous in nature, whereas naturally occurring peptide ligases, enzymes catalyzing the reverse reactions of proteases, are rare occurrences. Here we describe the discovery of butelase 1, to our knowledge the first asparagine/aspartate (Asx) peptide ligase to be reported. This highly efficient enzyme was isolated from Clitoria ternatea, a cyclic peptide-producing medicinal plant. Butelase 1 shares 71% sequence identity and the same catalytic triad with legumain proteases but does not hydrolyze the protease substrate of legumain. Instead, butelase 1 cyclizes various peptides of plant and animal origin with yields greater than 95%. With Kcat values of up to 17 s(-1) and catalytic efficiencies as high as 542,000 M(-1) s(-1), butelase 1 is the fastest peptide ligase known. Notably, butelase 1 also displays broad specificity for the N-terminal amino acids of the peptide substrate, thus providing a new tool for C terminus-specific intermolecular peptide ligations.

A physical map has been constructed of the human genome containing 15,086 sequence-tagged sites (STSs), with an average spacing of 199 kilobases. The project involved assembly of a radiation hybrid map of the human genome containing 6193 loci and incorporated a genetic linkage map of the human genome containing 5264 loci. This information was combined with the results of STS-content screening of 10,850 loci against a yeast artificial chromosome library to produce an integrated map, anchored by the radiation hybrid and genetic maps. The map provides radiation hybrid coverage of 99 percent and physical coverage of 94 percent of the human genome. The map also represents an early step in an international project to generate a transcript map of the human genome, with more than 3235 expressed sequences localized. The STSs in the map provide a scaffold for initiating large-scale sequencing of the human genome.

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