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D Ammer

Publications and source records attributed to D Ammer.

9 recordsLinked to original sources
PubMed1982

Comparison of amino acid sequence and thermostability of tyrosinase from three wild type strains of Neurospora crassa.

The thermostability of tyrosinase from three wild type strains of Neurospora crassa has been investigated. For this purpose a sequence comparison of two thermostable and one thermolabile tyrosinase isoenzyme was carried out. It revealed that at position 201 the thermostable enzyme forms share an aspartate residue in contrast to an asparagine residue in the thermolabile form. In addition, one of the thermostable isoenzymes displays five other substitutions. Since the relative stability of the thermostable forms as compared to the thermolabile one decreases with increasing ionic strength, the common aspartate residue is thought to bring about the additional stability of the thermostable isoenzymes by forming a salt bridge between aspartate 201 and a positively charged group of the protein. The strong pH-dependency of the thermostability with an apparent pKA of 6.6 indicates a histidinium side chain as the most likely ionic group to be involved in the salt bridge. This conjecture is also supported by measurements of the stability towards the chaotropic agent guanidinium chloride. The difference of the free energy change of denaturation delta GDH2O between the apoenzymes of a thermostable and a thermolabile isoenzyme was calculated as 2.5 kcal mol-1. Furthermore, it was shown that the copper ions of the native and the cobalt ions of Co(II)-substituted tyrosinase strongly enhance the stability of the protein as compared to its apoform.

Amino Acid Sequence↗
PubMed1982

Crab metallothionein. Primary structures of metallothioneins 1 and 2.

The complete amino acid sequences of metallothioneins 1 and 2 from the crab Scylla serrata are reported. The primary structures were determined by automated and manual sequence analysis on fragments produced by cleavage of the S-pyridylethylated, S-aminoethylated, and S-carbamidomethylated proteins with trypsin. The two isoproteins consist of 58 and 57 amino acid residues, respectively, and show a sequence identity of 83%. Comparison of their primary structures with the known sequences of three representative mammalian metallothioneins and Neurospora copper metallothionein reveals a high degree of sequence homology among the six proteins. The abundant cysteinyl residues were found to be strongly conserved, in agreement with their function as metal ligands (see following paper by Otvos, J. D., Olafson, R. W., and Armitage, I. M. (1982). J. Biol. Chem. 257, 2427-2431.

Amino Acid Sequence↗
PubMed1981

Amino acid sequence of copper-zinc superoxide dismutase from horse liver.

The complete amino acid sequence of copper-zinc superoxide dismutase from horse liver is reported. The molecule consists of 153 amino acids and has a Mr = 16,000. The primary structure was determined by automated and manual sequence analysis on fragments produced by cleavage of the S-carboxymethylated protein with cyanogen bromide and on peptides obtained by digestion with trypsin, thermolysin, Staphylococcus aureus protease, or subtilisin. The protein is devoid of tryptophan and tyrosine and displays an acetylated NH2 terminus. Comparison of its primary structure with the known sequences of copper-zinc superoxide dismutases from bovine and human erythrocytes and from yeast reveals a high degree of sequence homology among the four enzymes. This is especially borne out in the regions containing the amino acid residues involved in the metal binding and the half-cystine residues forming the intramolecular disulfide bridge. The striking conservation of the preponderant glycine residues known to be important for the pronounced protein folding in bovine erythrocyte superoxide dismutase suggests similar three-dimensional structures for human erythrocyte, horse liver, and yeast copper-zinc superoxide dismutases.

Amino Acid Sequence↗