N. Martin Young

The carbohydrate specificity of conglutinin and its homology to proteins in the hepatic lectin family

Inhibition experiments with D-mannose oligosaccharides establish that conglutinin recognises terminal alpha 1----2 mannobiosyl units present in the glycopeptide of the alpha-chain of the complement component C3b. On the basis of its three domain structure and the homology of its N-terminal amino-acid sequence to that of the dog pulmonary surfactant protein, it is proposed that conglutinin is a member of the hepatic lectin family.

Comparison of three phosphorylcholine-binding mouse myeloma proteins by circular dichroism.

Summary Circular dichroic spectra of MOPC 167, McPC 603 and TEPC 15 mouse 1gA myeloma proteins in their polymeric and monomeric forms demonstrate that the MOPC 167 protein is quite distinct in structure while the other two show considerable similarity. The differences reside in the Fab portions of the proteins. Binding of phosphorylcholine produced the greatest change in the aromatic region of the spectrum of TEPC 15 monomer and the much more weakly bound hapten, choline, gave virtually the same spectral changes.

The amino acid sequences of two putative copper-site peptides from the "blue" copper protein, stellacyanin.

Abstract The sequences of a thirteen residue glycopeptide containing the sole cysteine residue of stellacyanin and a pentapeptide containing histidine were determined by the dansyl-Edman method. There is relatively little homology between stellacyanin and plastocyanin or azurin in the cys region and the adjacent histidine proposed as a ligand to Cu in plastocyanin and azurin is absent in stellacyanin. There are homologies between the Cu subunit of cytochrome oxidase and these “blue” copper proteins, in this region. The his peptide shows homologies with the sequence around an invariant his in plastocyanin.

Modification of aspartic acid residues to induce trypsin cleavage

1,2-Diaminoethane and diaminomethane were coupled to aspartic acid residues in small peptides by means of a water-soluble carbodiimide. The resulting modified side chains sufficiently resembled lysine for trypsin to cleave the peptides. Similar modification of glutamic acid residues in peptides gave little or no susceptibility to trypsin.

The dinitrophenyl group as a selective label in high-performance liquid chromatography of peptides.

1-Fluoro-2,4-dinitrobenzene can be used to selectively label histidine, tyrosine, and cysteine residues in maleylated proteins. The usefulness of the resulting chromophores for peptide mapping by high-performance liquid chromatography was demonstrated with the lectin from sainfoin (Onobrychis viciifolia). The 2,4-dinitrophenyl (Dnp) label also can be used in a hydrophobic modulation approach as the mobility of a labeled model peptide changes considerably when its Dnp group is removed by thiolysis. Application of the method for checking sequences obtained by DNA or amino acid methods was shown by experiments with Viciae lectins. The probable cleavage site that generates the pea lectins beta-chain from the alpha-beta precursor was identified and the sequence differences between the lentil and pea lectin beta-chains were examined.

Application of high-performance liquid chromatography to competitive labeling studies: The chemical properties of functional groups of glucaton

Abstract A competitive-labeling study of glucagon was carried out using [ 3 H]- and [ 14 C]-1-fluoro-2,4-dinitrobenzene to determine simultaneously the chemical properties of the α-amino and imidazole groups of the N-terminal histidine residue, and the lysine and tyrosine residues, under conditions where glucagon is in its physiologically active monomer form. The dinitrophenyl derivatives of these groups were purified by high-performance liquid chromatography which greatly simplified the separation steps of the procedure. The results showed the α-amino and tyrosine groups to have relatively normal behavior, with p K values of 7.98 and 10.22, respectively, while the lysine had a low p K of 8.46. The imidazole function had an apparent p K of 7.84, substantially higher than previous estimates. This difference may be accounted for by the effect of the charged form of the adjacent α-amino group on the nucleophilicity of the imidazole group.

Reaction of the oligomeric forms of MOPC 167 IgA with antigen and a circular dichroism study of the binding of pneumococcal C substance by monomer IgA

Abstract The roles of multivalence and conformational change in the reactions of the various oligomeric forms of MOPC 167 IgA with phosphorylcholine-containing antigens were studied. The oligomeric forms of MOPC 167 IgA were separated by affinity chromatography with gradient elution. There was a linear relationship between the size of the oligomer and the hapten concentration required for its elution from the column. In precipitation experiments, the dimer and tetramer forms gave very similar behaviour with pneumococcal C substance, but the tetramer required more than twice as much hapten for inhibition of precipitation. In a passive hemagglutination system, the activities of monomer, dimer and tetramer were in the proportions 1:8:128. In reverse radial immunodiffusion tests, the dimer was twice as active as the tetramer. Therefore the multivalence of the oligomeric forms of IgA confers only modest increases in overall binding affinity. When pneumococcal C substance was added to monomer MOPC 167 IgA no change was detected in the C.D. spectrum in either the aromatic or far u.v. regions. A small change attributable to a tyrosine residue occurred when phosphorylcholine was added. The same results were obtained with MOPC 167 Fab, hence no conformational change in Fc chromophores was triggered by combination with antigen.