PROTEIN INTERACTIONS IN THE CALF EYE LENS - INTERACTIONS BETWEEN BETA-CRYSTALLINS ARE REPULSIVE WHEREAS IN GAMMA-CRYSTALLINS THEY ARE ATTRACTIVE

Non-specific interactions in beta- and gamma-crystallins have been stu died by solution X-ray scattering and osmotic pressure experiments. Me asurements were carried out as a function of protein concentration at two ionic strengths. The effect of temperature was tested between 7-de grees-C and 31-degrees-C. Two types of interactions were observed. Wit h beta-crystallin solutions, a repulsive coulombic interaction could b e inferred from the decrease of the normalized X-ray scattering intens ity near the origin with increasing protein concentration and from the fact that the osmotic pressure increases much more rapidly than in th e ideal case. As was previously observed with alpha-crystallins, such behaviour is dependent upon ionic strength but is hardly affected by t emperature. In contrast, with gamma-crystallin solutions, the normaliz ed X-ray scattering intensity near the origin increases with increasin g protein concentration and the osmotic pressure increases less rapidl y than in the ideal case. Such behaviour indicates that attractive for ces are predominant, although we do not yet know their molecular origi n. Under our experimental conditions, the effect of temperature was st riking whereas no obvious contribution of the ionic strength could be seen, perhaps owing to masking by the large temperature effect. The re levance of the different types of non-specific interactions for lens f unction is discussed.