Peptide ligands for a sugar-binding protein isolated from a random peptide library.

Abstract

Peptide Carbohydrate-protein interactions form the basis of a host of biological processes (1, 2). For example, the periplasmic monosaccharide-binding proteins of Gram-negative bacteria serve as receptors for transport and chemotaxis (3), while cell-surface lectins mediate such processes as cell-cell adhesion (4, 5) and lymphocyte migration through lymphoid tissues (6). Carbohydrate recognition is central to the enzymatic synthesis and degradation of polysaccharides, glycoproteins, and glycolipids that play essential roles in metabolism and in the maintenance of cellular structures. Carbohydrate-protein associations are also critical in certain cycles of viral infection. For example, binding of the hemagglutinin protein of human influenza virus to sialic acid residues on erythrocyte cell-surface glycoproteins represents the initial step in influenza infection (7).Consequently, the development of potent inhibitors of carbohydrate-specific proteins may be of considerable importance in the generation of new therapeutic agents. However, the synthesis of complex carbohydrate ligands and analogs often requires many time-consuming, low-yielding steps. Chemical synthesis of oligosaccharides requires sophisticated strategies for protecting/deprotecting and assembling sugar monomers and for controlling product regiochemistry and stereochemistry (8-10). Enzymatic synthesis using glycosyltransferases has emerged as a useful alternative to chemical synthesis (11,12). However, this approach is limited by the availability of enzymes with the appropriate specificities.An alternative approach to the synthesis of polysaccharide ligands for carbohydrate-specific receptors is to ask whether peptides can be found that bind these proteins with high affinities. We describe a strategy for identifying novel peptide ligands for carbohydrate-binding proteins based on the screening of a large, highly diverse peptide library expressed on the surface of filamentous phage fd (13-16). The library consists of phage bearing random octapeptides fused to the amino terminus of the minor coat protein, pIII, and was screened by affinity purification on immobilized receptor. We chose as a model system the lectin Con A fromjack bean, whose physicochemical properties have been extensively studied (17). Con A is a tetramer composed of four identical polypeptide chains consisting of 237 residues each. Con A, which interacts preferentially with oligosaccharides bearing terminal a-linked mannose or glucose residues, is frequently employed in the purification and structural characterization of carbohydrates and glycoproteins and is also a lymphocyte mitogen. We report the isolation of peptide ligands for Con A that prevent binding of known monosaccharide ligands of the lectin and that inhibit Con A-dependent precipitation of polysaccharides. The prospect that specific ligands for carbohydrate-binding proteins can be assembled by coupling amino acid building blocks (rather than sugars) should greatly reduce the synthetic difficulties associated with i...

Structural Basis of GD2 Ganglioside and Mimetic Peptide Recognition by 14G2a Antibody

“…The fact that peptides can mimic carbohydrates in their binding to target proteins has been first demonstrated by Oldenburg and colleagues (43). Given the diverse potential applications of such peptides, a significant number of mimetics have been described since.…”

Induction of IgG antibodies against the GD2 carbohydrate tumor antigen by vaccination with peptide mimotopes

“…It is a technique to define peptides mimicking natural epitopes, including carbohydrate structures [34][35][36]. Phage display peptide libraries consist of filamentous phage particles displaying random peptides of defined length on their surface.…”

Structural Evaluation of a Mimicry-Recognizing Paratope: Plasticity in Antigen–Antibody Interactions Manifests in Molecular Mimicry

“…Methyl a-D-mannopyranoside and a dodecapeptide (DVFYPY-PYASGS) known to bind Con A with comparable affinities have been studied extensively as a model system to address molecular mimicry in the humoral immune response (17)(18)(19). Polyclonal sera generated against methyl a-D-mannopyranoside cross-recognize the dodecapeptide, and correspondingly antipeptide sera cross-react with the mannopyranoside (20).…”