Intermolecular protein interactions in solutions of calf lens alpha-crystallin. Results from 1/T1 nuclear magnetic relaxation dispersion profiles

Abstract

From analyses of the magnetic field dependence of 1/T1 (NMRD profiles) of water protons in solutions of calf lens alpha-crystallin at several concentrations, we find two regimes of solute behavior in both cortical and nuclear preparations. Below approximately 15% vol/vol protein concentration, the solute molecules appear as compact globular proteins of approximately 1,350 (cortical) and approximately 1,700 (nuclear) kD. At higher concentrations, the effective solute particle size increases, reversibly, as evidenced by the appearance of spectra-like 14N peaks in the NMRD profiles and a change in the field and temperature dependence of 1/T1. At these higher concentrations, the profiles are very similar to those of calf gamma II-crystallin, a crystallin that undergoes an analogous transition near approximately 15% protein (Koenig, S. H., C.F. Beaulieu, R. D. Brown III, and M. Spiller, 1990. Biophys. J. 57:461-469). By comparison with recent analyses of NMRD results for solutions of immobilized proteins as models for the transition from protein solutions to tissue (Koenig, S. H., and R. D. Brown III. 1991. Prog. NMR Spectr. 22:487-567), we argue that alpha-crystallin solute behaves as aggregates approximately greater than 50,000 kD as protein concentration is progressively increased above 15%. Finally, the concentration dependence of the NMRD profiles of alpha- and gamma II-crystallin can readily explain recent osmotic pressure data, in particular the intersection of the respective pressure curves at approximately 23% vol/vol (Vérétout, F., and A. Tardieu. 1989. Eur. Biophys. J. 17:61-68).

A Small‐Angle Neutron Scattering Study of γ‐Crystallins Near Their Isoelectric Point

“…We can conclude that there is a temperature-induced aggregation or temporal associations but we cannot quantify them. Recently, Koenig et al found that 7-crystallin fractions aggregate as the temperature decreases (Koenig et a]., 1990(Koenig et a]., , 1992. They claim that the phase transition observed in y-crystallin solutions is driven by the formation of these protein aggregates.…”

Biochemical Characterization of the Small Heat Shock Protein IbpB from Escherichia coli

“…The eye lens protein ␣-crystallin, which has a dynamic oligomeric structure (44,45), has also been isolated as distinct populations in the 600 -900-kDa, 900-kDa-4-MDa, and greater than 10-MDa ranges (46). However, because concentration, pH, ionic strength, and temperature of isolation have all been reported to affect the oligomeric state of ␣-crystallins (47,48) and because IbpA may modulate the quaternary structure of IbpB, it is not clear whether large IbpB oligomers also exist in vivo.…”

Magnetization transfer in cross‐linked bovine serum albumin solutions at 200 MHz: A model for tissue

“…YO solids. ;l In contrast to solutions of mobile protein, the functional form of the dispersions ( 5 2 0 MHz) of 1/T, of immobile protein and tissue (there are few data for 1/T,) is different in several characteristic ways (29): both the temperature dependence and the change upon deuteration of solvent are much reduced; the T,/T, ratio is much enhanced at higher fields; and 14N peaks generally become prominent. These distinctions arise from an increase in the importance of magnetization transfer across the protein-water interface upon immobilization, which then is the major determinant of the observed NMRD profiles.…”