Alpha crystallin
Alpha crystallin is a water-soluble structural protein found in the lens of the eye. Compared to the other crystallins, it elutes earlier from a gel filtration chromatography column.
The crystallins are water-soluble structural proteins that occur in high concentration in the cytoplasm of eye lens fiber cells. Four major groups of crystallin have been distinguished on the basis of size, charge and immunological properties: alpha-, beta- and gamma-crystallins occur in all vertebrate classes (though gamma-crystallins are low or absent in avian lenses); and delta-crystallin is found exclusively in reptiles and birds[1][2].
Alpha-crystallin occurs as large aggregates, comprising two types of related subunits (A and B) that are highly similar to the small (15-30kDa) heat shock proteins (HSPs), particularly in their C-terminal halves. The relationship between these families is one of classic gene duplication and divergence, from the small HSP family, allowing adaptation to novel functions. Divergence probably occurred prior to evolution of the eye lens, alpha-crystallin being found in small amounts in tissues outside the lens[1].
Alpha-crystallin has chaperone-like properties including the ability to prevent the precipitation of denatured proteins and to increase cellular tolerance to stress[3]. It has been suggested that these functions are important for the maintenance of lens transparency and the prevention of cataracts[4]. This is supported by the observation that alpha-crystallin mutations show an association with cataract formation.
The N-terminal domain of alpha-crystallin is not necessary for dimerisation or chaperone activity, but appears to be required for the formation of higher order aggregates[5][6].
References
- ^ a b de Jong WW, Bloemendal H, Hendriks W, Mulders JW (1989). "Evolution of eye lens crystallins: the stress connection". Trends Biochem. Sci. 14 (9): 365–8. doi:10.1016/0968-0004(89)90009-1. PMID 2688200.
- ^ Simpson A, Bateman O, Driessen H, Lindley P, Moss D, Mylvaganam S, Narebor E, Slingsby C (1994). "The structure of avian eye lens delta-crystallin reveals a new fold for a superfamily of oligomeric enzymes". Nat. Struct. Biol. 1 (10): 724–734. doi:10.1038/nsb1094-724. PMID 7634077.
- ^ Augusteyn RC (2004). "alpha-crystallin: a review of its structure and function". Clin Exp Optom 87 (6): 356–66. PMID 15575808.
- ^ Maulucci G, Papi M, Arcovito G, De Spirito M (2011). "The Thermal Structural Transition of α-Crystallin Inhibits the Heat Induced Self-Aggregation". PLoS One 6 (5): e18906. doi:10.1371/journal.pone.0018906.
- ^ Augusteyn RC (1998). "alpha-Crystallin polymers and polymerization: the view from down under". Int. J. Biol. Macromol. 22 (3): 253–62. PMID 9650080.
- ^ Malfois M, Feil IK, Hendle J, Svergun DI, van Der Zandt H (2001). "A novel quaternary structure of the dimeric alpha-crystallin domain with chaperone-like activity". J. Biol. Chem. 276 (15): 12024–12029. doi:10.1074/jbc.M010856200. PMID 11278766.
This article incorporates text from the public domain Pfam and InterPro IPR003090
Human proteins containing this domain
CRYAA; CRYAB;
External links
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Chaperones/
protein folding |
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Hsp10/GroES (Early pregnancy factor) · Hsp27 · Hsp47 · HSP60/GroEL
Hsp40/DnaJ (A1, A2, A3, B1, B2, B11, B4, B6, B9, C1, C3, C5, C6, C7, C10, C11, C13, C14, C19)
Hsp70 (1A, 1B, 1L, 2, 4, 4L, 5, 6, 7, 8, 9, 12A, 14)
Hsp90 ( α1, α2, β, ER, TRAP1)
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Other
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| Ubiquitin |
E1 Ubiquitin-activating enzyme (UBA1, UBA2, UBA3, UBA5, UBA6, UBA7, ATG7, NAE1, SAE1)
E2 Ubiquitin-conjugating enzyme (A • B • C • D1, D2, D3 • E1, E2, E3 • G1, G2 • H • I • J1, J2 • K • L1, L2, L3, L4, L6 • M • N • O • Q1, Q2 • R1 (CDC34), R2 • S • V1, V2 • Z)
E3 Ubiquitin ligase (VHL, Cullin, CBL, MDM2, FANCL, UBR1)
Deubiquitinating enzyme: Ataxin 3 • USP6 • CYLD
ATG3 • BIRC6 • UFC1
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see also posttranslational modification disorders
B bsyn: dna (repl, cycl, reco, repr) · tscr (fact, tcrg, nucl, rnat, rept, ptts) · tltn (risu, pttl, nexn) · dnab, rnab/runp · stru (domn, 1°, 2°, 3°, 4°)
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| Opsin (retinylidene protein) |
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| Crystallin |
Alpha ( A, B) · Beta ( A1, A2, A4, B1, B2, B3) · Gamma ( A, B, C, D, N, S) |
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anat(g/a/p)/phys/devp/prot
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