High-performance gel permeation chromatography of bovine eye lens proteins in combination with low-angle laser light scattering : Superior resolution of the oligomeric β-crystallins

Abstract

Calf lens extracts were subjected to high-performance gel permeation chromatography on TSK GEL G4000 SW and G3000 SW columns (fractionation range: 5 ṡ 10 6–10 4 daltons) and resolved into thirteen crystallin fractions: HM-, α-, six β H-, two β L-,β S-, and two γ-crystallins. Molecular weights were determined using a low-angle laser light scattering detection system. The weight average and number average molecular weights for cortical α-crystallin, 860,000 and 740,000, respectively, reveal a polydispersity factor of 1.16 for this heterogeneous protein. The eight different β-crystallin fractions could be found with practically all possible oligomeric structures from dimers to aggregates larger than dodecamers. Different structures are found for the predominant β H-crystallin fractions, viz., hexamers and pentamers, in the extracts from cortex and nucleus, Additional identification of the fractions by sodium dodecyl sulphate gel electrophoresis and isoelectric focusing in the presence of urea also indicated that semi-preparative application of this high-performance technique is possible. The co-elution of putative cytoskeletal proteins with some β-crystallins was remarkable; moreover, co-elution of FM-crystallin with β S-crystallin is discussed. A 23,000-dalton fraction, mainly found in the cortical region, most likely corresponds to the 24,000-dalton γ-crystallin preparation obtained from cattle lens cortices. It is questioned whether the similarities between this fraction and β S-crystallin are merely coincidental.