Chemische Analyse und Struktur des Poliovirus. I. Cystein/Cystin Gehalt, vollständige Aminosäureanalyse und Hydrophobizität von Poliovirus und seinen natürlichen leeren Kapsiden / Chemical Analysis and Structure of Poliovirus. I. Cysteine/Cystine Content, Complete Amino Acid Analysis and Hydrophobicity of Poliovirus and Its Naturally Occurring Empty Capsids
2014
Heukeshoven, Jochen | Demick, Rudolf
The cysteine content of poliovirus particles and naturally occuring empty capsids was determined by two methods: (1) reaction with vinylpyridine and subsequent amino acid analyses and (2) treatment with 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) and measurement in the change of absorption. Both methods were performed under dissociating conditions in order to expose all sulfhydryl groups. Poliovirus, type 1, strain Mahoney, contains 10-11 cysteine/cystine residues per protomer, irrespective of the use of virus particles or empty capsids. Poliovirus, type 3, strain Saukett, contains 12-13 cysteine/cystine residues per protomer. Poliovirus particles are completely free of disulfide bridges, whereas empty capsids contain 2-4 cystine residues/protomer. No sulfhydryl groups are present on the surface of the virus particle, because of lack of reaction with DTNB. The tryptophan content was determined to be 13 ± 1 residues/protomer. By amino acid analysis under controlled hydrolyzing conditions 12 residues/protomer were found, whereas formylation in hydrochloric acid/formic acid revealed 14 residues/protomer; 13 tryptophan residues were calculated from the tyrosine-tryptophan relation and the optical density at 293.5 nm and 280 nm. The following parameters of poliovirus particles were calculated from the improved and complete amino acid analysis and the cysteine and tryptophan content: 1. The molecular weight of a protomer to be 92 700 ± 900 Dalton and of the poliovirus particle, type 1, strain Mahoney, to be 7.97 × 10⁶ Dalton. 2. The relative hydrophobicity of the poliovirus polypeptide to be 1.18. 3. The extinction coefficients of poliovirus E¹%₂₆₀ = 7 4 and of empty capsids E¹%₂₈₀ = 16.2 ± 0.2.
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