Intracellular Carboxy‐Terminal Degradation of the αA Chain of α‐Crystallin

Jong, Wilfried W. de; Kleef, Frans S.M. van; Bloemendal, H.

doi:10.1111/j.1432-1033.1974.tb03765.x

Cited by 59 publications

(6 citation statements)

References 22 publications

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“…My calculations show that, at an approximately stoichiometric concentration of enzymes to a-crystallin, heat aggregation is completely suppressed. This was the case with GroEL and a-glucosidase (20 (45)(46)(47)(48)(49)(50)(51)(52). The effects of all of these modifications on the function of a-crystallin in the lens and other tissues is yet to be determined.…”

Section: Discussionmentioning

confidence: 97%

Alpha-crystallin can function as a molecular chaperone.

Horwitz

1992

Proc. Natl. Acad. Sci. U.S.A.

1,699

1,199

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The a-crystallins (aA and aB) are major lens structural proteins of the vertebrate eye that are related to the small heat shock protein family. In addition, crystallins (especially aB) are found in many cells and organs outside the lens, and aB is overexpressed in several neurological disorders and in cell lines under stress conditions. Here I show that a-crystallin can function as a molecular chaperone. Stoichiometric amounts of aA and aB suppress thermally induced aggregation of various enzymes. In particular, a-crystalln is very efficient in suppressing the thermally induced aggregation of If-and y-crystallins, the two other major mammalian stural lens proteins. a-Crystallin was also effective in preventing aggregation and in refolding guanidine hydrochloride-denatured y-crystallin, as judged by circular dichroism spectroscopy. My results thus indicate that a-crystallin refracts light and protects proteins from aggregation in the transparent eye lens and that in nonlens cells a-crystallin may have other functions in addition to its capacity to suppress aggregation of proteins. a-Crystallin is one of the major lens structural proteins in the vertebrate eye. In mammalian lenses, a-crystallin can reach levels of "50% of the total lens structural protein mass (1). There are two genes in the a-crystallin family, one for aA-crystailin and one for aB-crystallin. Studies on the struc-

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Section: Discussionmentioning

confidence: 97%

Alpha-crystallin can function as a molecular chaperone.

Horwitz

1992

Proc. Natl. Acad. Sci. U.S.A.

1,699

1,199

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“…However, beside the normal Ai, AZ, Br and Bz bands some additional polypeptides were present as already observed by others [9-111. Studies on bovine a-crystallin have shown that in this species such additional bands, especially pronounced in the adult lens nucleus, represent postsynthetic modifications of the primary gene products AZ and Bz [5,12] . cu-Crystallin from normal and cataractous lenses showed essentially the same pattern.…”

Section: Resultsmentioning

confidence: 99%

The amino acid sequence of the A chain of human α‐crystallin

Jong¹,

Terwindt²,

Bloemendal³

1975

FEBS Letters

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“…Several truncation products have been characterized. aA-crystallin is processed age-dependently by cleavage at various amino acids in the C-terminal half of the molecule resulting in the polypeptides aA(1-172) [177], aA(1-169), aA(1-168) [178], aA(1-151) [179] and aA(1-101) [180].…”

Section: Truncationmentioning

confidence: 99%

Structure and Modifications of the Junior Chaperone α‐Crystallin

Groenen

Merck

Jong

et al. 1994

European Journal of Biochemistry

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350

260

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alpha-Crystallin is a high-molecular-mass protein that for many decades was thought to be one of the rare real organ-specific proteins. This protein exists as an aggregate of about 800 kDa, but its composition is simple. Only two closely related subunits termed alpha A- and alpha B-crystallin, with molecular masses of approximately 20 kDa, form the building blocks of the aggregate. The idea of organ-specificity had to be abandoned when it was discovered that alpha-crystallin occurs in a great variety of nonlenticular tissues, notably heart, kidney, striated muscle and several tumors. Moreover alpha B-crystallin is a major component of ubiquinated inclusion bodies in human degenerative diseases. An earlier excitement arose when it was found that alpha B-crystallin, due to its very similar structural and functional properties, belongs to the heat-shock protein family. Eventually the chaperone nature of alpha-crystallin could be demonstrated unequivocally. All these unexpected findings make alpha-crystallin a subject of great interest far beyond the lens research field. A survey of structural data about alpha-crystallin is presented here. Since alpha-crystallin has resisted crystallization, only theoretical models of its three-dimensional structure are available. Due to its long life in the eye lens, alpha-crystallin is one of the best studied proteins with respect to post-translational modifications, including age-induced alterations. Because of its similarities with the small heat-shock proteins, the findings about alpha-crystallin are illuminative for the latter proteins as well. This review deals with: structural aspects, post-translational modifications (including deamidation, racemization, phosphorylation, acetylation, glycation, age-dependent truncation), the occurrence outside of the eye lens, the heat-shock relation and the chaperone activity of alpha-crystallin.

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Intracellular Carboxy‐Terminal Degradation of the αA Chain of α‐Crystallin

Cited by 59 publications

References 22 publications

Alpha-crystallin can function as a molecular chaperone.

Alpha-crystallin can function as a molecular chaperone.

The amino acid sequence of the A chain of human α‐crystallin

Structure and Modifications of the Junior Chaperone α‐Crystallin

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