Effect of boronic acids on antifreeze proteins.

The activity of antifreeze glycoprotein from the blood serum of Boreagadus saida was strongly inhibited by ions of organic boronic acids as well as by borate. The activity of nonglycoprotein from the blood serum of Pseudopleuronectus americanus, however, was not similarly inhibited. The inhibition by borate is thus specific for molecules with the carbohydrate moiety.

Modification of galactose and N-acetylgalactosamine residues by oxidation of C-6 hydroxyls to the aldehydes followed by reductive amination: model systems and antifreeze glycoproteins.

Amino acids and peptides have been attached to the C-6 hydroxyls of the galactose and the N-acetylgalactosamine by first oxidizing the C-6 hydroxyls to the aldehydes by galactose oxidase in the presence of small amounts of catalase, followed by reductive amination (alpha-amino group) in the presence of cyanoborohydride. The activity of oxidized antifreeze glycoprotein was greater than 70% of the original, and considerable activity has been retained with some substitutions on reductive amination using cyanoborohydride. The following were some activities retained (as compared with the oxidized antifreeze glycoprotein): Gly, 64; (Gly)2, 88; (Gly)3, 82; (Gly)4, 70; Gly-Gly-NH2, 44; Gly-Glu, 13; Gly-Leu, 40; Gly-Tyr, 57; Gly-Gly-Leu, 50; Gly-Gly-Phe, 30; and Gly-Gly-Val, 35.

Egg-white and blood-serum proteins functioning by noncovalent interactions: studies by chemical modification and comparative biochemistry.

Some of the more interesting and important proteins are those that function by forming associations or complexes with other substances. The structure-function relationships of three of these with very different substances are transferrins, which chelate metal ions; avian ovomucoids, which form complexes with proteolytic enzymes; and antifreeze glycoproteins, which interact at the ice-solution interface. Interrelating studies on the comparative biochemistry with studies using chemical modification have helped identify the side-chain groups of the proteins involved in function as well as to be useful for studies on general protein chemistry.

The interaction of anions with native and phenylglyoxal-modified human serum transferrin.

The interaction of various anions with human serum transferrin was investigated due to the concomitant binding of iron and a synergistic anion to form the transferrin-anion-iron complex. Two tetrahedral oxyanion oxidizing agents, periodate and permanganate, were found to partially inactivate transferrin when used at equimolar ratios of oxidizing agent to protein active sites. Hypochlorite, a strong oxidizing agent with little structural similarity to periodate and permanganate, had little effect on iron-binding activity when used at similar low molar ratios of reagent to transferrin active sites.

A kinetic description of antifreeze glycoprotein activity.

The antifreeze glycoproteins (AFGP) of polar fish have the ability to depress the freezing temperature of water approximately 500 times the amount expected based on the number of AFGP molecules in solution; yet AFGP solutions have a purely colligative melting point depression. The difference of solution melting and freezing temperatures is the antifreeze activity of AFGP. One characteristic of AFGP activity that requires further examination is the effect of concentration on antifreeze activity, especially whether the activity saturates at high concentrations or the measured activity increases ad infinitum.

Purification and primary sequences of the major arginine-containing antifreeze glycopeptides from the fish Eleginus gracilis.

An Arg-containing antifreeze glycoprotein from the polar fish Eleginus gracilis was isolated, and the major components were purified to homogeneity. The general protocol for purification was chromatography of serum on DEAE-cellulose, followed by chromatography on a cation exchanger. DEAE-cellulose chromatography resulted in two fractions, A and B.

1-Deoxyglycitolation of protein amino groups and their regeneration by periodate oxidation.

Reductive alkylation of lysyl epsilon-amino groups with sugars (1-deoxyglycitolation) using pyridine borane as the reducing agent has been recently described [Wong, W.S.D.

Interaction of oxidized chicken ovotransferrin with chicken embryo red blood cells.

Iron-saturated chicken ovotransferrin was chemically oxidized with NaIO4, converting 50% of its methionine residues to their sulfoxide derivatives while maintaining 95% of its iron-binding activity. The oxidized chicken ovotransferrin was able to deliver iron to the chicken embryo red blood cell for heme synthesis. From competition experiments, oxidized diferric chicken ovotransferrin was estimated to be approx.

Determination of tryptophan as the reduced derivative by acid hydrolysis and chromatography.

A new procedure for the analyses of tryptophan and the total amino acid composition of proteins was based on the observations that pyridine borane reduces tryptophan in trifluoroacetic acid, while other amino acids remain intact [M. Kurata, Y. Kikugawa, T.

Conformation of the antifreeze glycoprotein of polar fish.

High-field proton and 13C NMR spectroscopy has been used to test and refine the recent proposal, based on vacuum uv circular dichroism results, of a threefold left-handed helical conformation for antifreeze glycoprotein (AFGP). Partial assignment of the protons of the glycotripeptide repeating unit has been made by comparison with spectra of model compounds, by selective decoupling, and by measurements of nuclear Overhauser effect (nOe). At 40 degrees C, AFGP fraction 8 (Mr 2600) shows 2-Hz linewidths which broaden at lower temperature.

Analysis of antifreeze glycoproteins in fish serum.

A procedure utilizing high-pressure size-exclusion chromatography that permits rapid screening for both the types of components present in and the quantity of antifreeze glycoprotein in fish serum or solution is described. The applicability of the method is demonstrated by a comparative study of five different fish species, four of which contain the antifreeze glycoprotein and one which does not contain this protein. The antifreeze glycoprotein compositions of two fish of the same species, collected at different locations or under different environmental conditions, are also compared.

Pyridine borane as a reducing agent for proteins.

Pyridine borane has been reported as a superior reagent over a wide pH range, 5-9, for the reductive methylation of amino groups of proteins with formaldehyde [J. C. Cabacungan , A.

Comparative oxidations of tyrosines and methionines in transferrins: human serum transferrin, human lactotransferrin, and chicken ovotransferrin.

Periodate treatments of apo human serum transferrin (HST), and apo chicken ovotransferrin (COT) were previously reported to cause a rapid loss of Fe+3 binding capacity, with a loss of 3 to 5 tyrosine residues [P. AZARI AND J. L.

Antifreeze glycoprotein. Conformational model based on vacuum ultraviolet circular dichroism data.

Circular dichroism spectra (CD) of an active fraction of antifreeze glycoprotein (AFGP) and of a lower molecular weight fraction which is less active are found to be similar in the wavelength range 170-230 nm. The contribution of the disaccharide side chain chromophores to the CD spectra of the glycoprotein is estimated from spectra of model oligosaccharides having similar structures. Comparison of the CD spectra of the peptide portion of AFGP to those of established model polypeptides suggests a 3-fold left-handed helix of the collagen type as the most likely conformation of the peptide.

Antifreeze glycoproteins from Polar fish. Effects of freezing conditions on cooperative function.

Antifreeze glycoproteins and glycopeptides that function noncolligatively contribute one-third of the freezing temperature depression in the blood serum of some polar fishes and enable them to survive at low temperature (-1.9 degree C). There are at least eight closely related glycoproteins and glycopeptides ranging in molecular weight from 32,000 to 2,600 and numbered 1 to 8 in order of decreasing size.

Cooperative functioning between antifreeze glycoproteins.

Antifreeze glycoproteins from polar fish bloods are a mixture of closely related components which differ structurally by size and by the presence of proline in the smaller components. Although the smaller components containing proline exist in higher amounts than do the larger ones, their presence puzzled investigators because they had very weak antifreeze activity. A very important function for these smaller components has now been found.

Evolution of flightless land birds on southern continents: transferrin comparison shows monophyletic origin of ratites.

A biochemical approach was used to study the evolution of ratite birds, i.e., the ostriches, rheas, cassowaries, emus, and kiwis.