Crystallin is essential not only for the maintenance of eye lens transparency, but also in the biology of other tissues. Eye lens alpha-crystallin exists as a heteropolymer composed of two homologous subunits, alpha A and alpha B. Despite the critical role of alpha-crystallin in many tissues, little is known regarding structural and functional significance of the two subunits. Herein, we describe a unique feature of alpha B-crystallin. At high temperatures (> 70 degrees C) not only alpha B-crystallin aggregates but also enhances the aggregation of other lens proteins. Intriguingly, alpha B-crystallin-mediated coaggregation at and above 70 degrees C involves beta- but not gamma-crystallin. Further, alpha A-crystallin, but not a mutant (F71L) alpha A-crystallin, prevented aggregation of alpha B-crystallin and also reduced coaggregation of alpha B- and beta-crystallin. These studies explain the rationale for the existence of alpha-crystallin heteropolymer with alpha A subunit as a major partner that is vital for lens transparency and provide insights into alpha B-crystallin-induced coaggregation which may have a bearing in some pathological conditions where alpha B-crystallin is overexpressed. (C) 2011 Elsevier Inc. All rights reserved.