Tryptophan Cluster Protects Human γD-Crystallin from Ultraviolet Radiation-Induced Photoaggregation In Vitro
Article first published online: 20 JUN 2013
© 2013 The Authors. Photochemistry and Photobiology published by Wiley Periodicals, Inc. on behalf of The American Society of Photobiology.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Photochemistry and Photobiology
Volume 89, Issue 5, pages 1106–1115, September/October 2013
How to Cite
Schafheimer, N. and King, J. (2013), Tryptophan Cluster Protects Human γD-Crystallin from Ultraviolet Radiation-Induced Photoaggregation In Vitro. Photochemistry and Photobiology, 89: 1106–1115. doi: 10.1111/php.12096
- Issue published online: 6 SEP 2013
- Article first published online: 20 JUN 2013
- Accepted manuscript online: 20 MAY 2013 05:05AM EST
- Manuscript Accepted: 12 MAY 2013
- Manuscript Received: 15 FEB 2013
- National Eye Institute. Grant Number: #EY015834
- NSF. Grant Number: 007031
Exposure to ultraviolet radiation (UVR) is a significant risk factor for age-related cataract, a disease of the human lens and the most prevalent cause of blindness in the world. Cataract pathology involves protein misfolding and aggregation of the primary proteins of the lens, the crystallins. Human γD-crystallin (HγD-Crys) is a major γ-crystallin in the nucleus of the human lens. We report here analysis of UVR-induced damage to HγD-Crys in vitro. Irradiation of solutions of recombinant HγD-Crys with UVA/UVB light produced a rise in solution turbidity due to polymerization of the monomeric crystallins into higher molecular weight aggregates. A significant fraction of this polymerized protein was covalently linked. Photoaggregation of HγD-Crys required oxygen and its rate was protein concentration and UVR dose dependent. To investigate the potential roles of individual tryptophan residues in photoaggregation, triple W:F mutants of HγD-Crys were irradiated. Surprisingly, despite reducing UVR absorbing capacity, multiple W:F HγD-Crys mutant proteins photoaggregated more quickly and extensively than wild type. The results reported here are consistent with previous studies that postulated that an energy transfer mechanism between the highly conserved pairs of tryptophan residues in HγD-Crys could be protective against UVR-induced photodamage.