Amino acid sequence and physico-chemical behavior of coat proteins of wild strain tobacco mosaic virus. II. Aggregation behavior and electric charge distribution in comparison to the strains vulgare and dahlemense

Summary The primary structures of the coat proteins of three strains of TMV were established (Anderer et al., 1965; Wittmann-Liebold u. Wittmann, 1963; Wittmann 1965; Rentschler part I of this paper). They differ from one another in 29, 35 and 40 positions. Since the primary structure of a protein determines its secondary and tertiary structure, the geometry of the subunits and the cause of aggregation were investigated to see how they were influenced by the primary structures.The aggregation of the native proteins as a function of pH and ionic strength was investigated by determining sedimentation coefficients. All three proteins showed a similar cause of aggregation.The geometry of the subunits was compared in experiments with mixed aggregates (Sarkar, 1960). The result was that the subunits of U2 were able to form mixed aggregates with dahlemense and vulgare subunits. From this one can conclude that the geometrical properties of the three subunits are very similar.The A-Protein, the larger aggregates, and protein denatured in 8 M urea differed in their charge distributions. The differences seem to be located in regions of the polypeptide chain where they cause no disturbances and where they do not affect the aggregation properties.How to visualize the striking similarity of aggregation behaviour in spite of the great differences in primary structures is discussed on the basis of the conception of Tanford (1962) and Epstein (1964).

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2. Teil einer Dissertation der Mathematisch-naturwissenschaftlichen Fakultät der Universität Tübingen.