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Biochim Biophys Acta Proteins Proteom. 2017 May;1865(5):604-618. doi: 10.1016/j.bbapap.2017.02.003. Epub 2017 Feb 4.

The impact of different mutations at Arg54 on structure, chaperone-like activity and oligomerization state of human αA-crystallin: The pathomechanism underlying congenital cataract-causing mutations R54L, R54P and R54C.

Author information

1
Protein Chemistry Laboratory (PCL), Department of Biology, Shiraz University, Shiraz, Iran.
2
Protein Chemistry Laboratory (PCL), Department of Biology, Shiraz University, Shiraz, Iran. Electronic address: ryousefi@shirazu.ac.ir.
3
Center for Nanotechnology in Drug Delivery and School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran.
4
Department of Pathology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
5
Institute of Biochemistry and Biophysics (IBB), The University of Tehran, Tehran, Iran.
6
Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky Ave. 33, bld. 2, Moscow 119071, Russia.

Abstract

A major part of cataractogenic mutations in human αA-Crystallin (αA-Cry) occurs at Arg residues. While Arg54 is highly conserved within different species, the cataractogenic mutations R54L, R54P and R54C have been recently identified in CRYAA gene, encoding human αA-Cry. The detailed structural and functional aspects, stability and amyloidogenic properties of αA-Cry were determined upon the above-mentioned missense mutations, using various spectroscopic techniques, gel electrophoresis, electron microscopy, size exclusion chromatography analyses, and chaperone-like activity assay. The different mutations at Arg54 result in diverse structural alterations among mutant proteins. In addition, the mutant proteins displayed reduced thermal stability, increased amyloidogenic properties and attenuated chaperone-like activity against aggregation of γ-Cry, catalase and lysozyme. The mutant proteins were also capable of forming larger oligomeric complexes with γ-Cry which is the natural partner of α-Cry in the eye lenses. The most significant structural and functional damages were observed upon R54L mutation which was also accompanied with increased oligomeric size distribution of the mutant protein. The cataractogenic nature of R54P mutation can be explained with its detrimental effect on chaperone-like activity, conformational stability and proteolytic digestibility of the mutant protein. Also, R54C αA-Cry displayed an important intrinsic propensity for disulfide protein cross-linking with significantly reduced chaperone-like activity against all client proteins. These mutations revealed a range of detrimental effects on the structure, stability and functional properties of αA-Cry which all together can explain the pathomechanisms underlying development of the associated congenital cataract disorders.

KEYWORDS:

Cataract; Chaperone; Crystallin; Protein aggregation; Protein stability; αA-crystallin

PMID:
28179137
DOI:
10.1016/j.bbapap.2017.02.003
[Indexed for MEDLINE]

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