Polypeptide chain pathway in γ‐crystallin IIIb from calf lens at 3 Å resolution

Chirgadze, Yu. N.; Sergeev, Yu. V.; Fomenkova, N.P.; Oreshin, V.D.

doi:10.1016/0014-5793(81)80892-7

Cited by 26 publications

(14 citation statements)

References 10 publications

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“…Unfortunately, the X-ray structures of calf y-111 and y-IV crystallin are not yet available to sufficient resolution to determine tryptophan residue positions with accuracy (18). However, the present conclusions are in agreement with those based on fluorescence quantum yield and emission maxima measurements ( 2 ) .…”

Section: Methodssupporting

confidence: 85%

Fluorescence quenching studies of the structures of calf gamma-II, III, and IV crystallins

Phillips

Borkman

1988

Current Eye Research

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The structures of the calf lens crystallin fractions gamma-II, gamma-III, and gamma-IV have been investigated using the fluorescence quenching method. The three crystallin fractions showed very large differences in the quenching rates of their fluorescent tryptophan residues, for quenching by acrylamide or iodide in pH 7.5 phosphate buffer solutions. The experimentally measured quenching rate constants were kq(II) = 3.2 x 10(8), kq(III) = 9.9 x 10(8), and kq(IV) = 1.8 x 10(9) M-1 sec-1. Smaller rate constants were obtained for iodide quenching of the three crystallins, but the values were in approximately the same ratios as the ones found for acrylamide quenching. The conclusion is that the tryptophan residues in gamma-II crystallin are 6-10 times less easily quenched than those of gamma-IV crystallin and 3-6 times less easily quenched than those of gamma-III. These conclusions are in accord with those reached by Mandal et. al. based on fluorescence and CD data, who found the following order of Trp hydrophobicities: gamma-II greater than gamma-III greater than gamma-IV. The significance of these structural differences for lens function and stability remains to be elucidated.

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Section: Methodssupporting

confidence: 85%

Fluorescence quenching studies of the structures of calf gamma-II, III, and IV crystallins

Phillips

Borkman

1988

Current Eye Research

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“…40 amino acids in antiparallel P-pleated sheet structure [3,4,8]. A similar structure is found in bovine y-111 [9] and y-IV [lo] crystallins.…”

Section: Introductionsupporting

confidence: 54%

A computer graphics model of frog γ‐crystallin based on the three‐dimensional structure of calf γ‐II crystallin

et al. 1986

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Molecular models for Rana y-l and y-2 crystallins have been constructed using computer graphics on the basis of the protein primary structure derived from the complementary DNA sequence and the three-dimensional structure of calf y-11 crystallin that has been defined at high resolution by X-ray analysis. The models show that the cores of the two domains are conserved as hydrophobic, with the polypeptide chain arranged as a four Greek-key motif structure. Although many lysines replace arginines at equivalent positions in mammalian proteins, the Rana crystallins also have an extensive series of ion pairs on their surface; these are strongly implicated in their function as stable structural molecules, which are highly conserved in the evolution of the vertebrate eye lens. y-CrystallinComputer graphics model

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“…Their amino acid compositions are very similar, and their primary sequences are highly homologous (8,16,17,43,44). Three-dimensional structure analysis by xray diffraction of yII-, yIIIa-, yIIIb-, and yIV-crystallin has either been reported or is in progress (19,(45)(46)(47). There is sufficient evidence that all have the same highly symmetrical, two-domain, antiparallel /3-sheet backbone structure as described in detail for yII-crystallin (45)(46)(47).…”

mentioning

confidence: 86%

“…Three-dimensional structure analysis by xray diffraction of yII-, yIIIa-, yIIIb-, and yIV-crystallin has either been reported or is in progress (19,(45)(46)(47). There is sufficient evidence that all have the same highly symmetrical, two-domain, antiparallel /3-sheet backbone structure as described in detail for yII-crystallin (45)(46)(47). The surface characteristics of individual y-crystallins will then contribute to the differences in their cryoprecipitation behavior.…”

mentioning

confidence: 99%

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

Siezen¹,

Fisch²,

Slingsby³

et al. 1985

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

113

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To determine the molecular mechanisms for cold cataract formation in the nucleus of the young mammalian lens, we have investigated the thermally reversible opacification of -crystallin solutions isolated from calf lens. Coexistence curves (plots of opacification temperature Tc versus protein concentration) were determined for the individual y-crystallin fractions II, III, and IV as well as for the unfractionated -crystallin mixtures isolated from the nucleus and cortex. The coexistence curve of yIV-crystallin is remarkably elevated above those of y4I-and yIII-crystallin and the -crystallin mixtures. The yIV-crystallin fraction is the major determinant of the opacification temperature within the whole lens or isolated cytoplasm. Quasielastic light-scattering spectroscopy of yIV-crystallin solutions indicates that above Tc there are two populations of protein aggregates of distinctly different mean size. As the temperature is lowered towards Tc, both populations increase in size. Opacification occurs when the population of large scatterers, which is composed of <0.1% protein by weight, reaches an average radius of about 20,000 A.The cytoplasm in eye lens cells contains a highly concentrated solution of lens-specific proteins, the crystallins. Their concentration increases from =250 to 400 g/liter going from cortex to nucleus, thus establishing the refractive index gradient required for proper focusing of incident light (1). The cytoplasm is normally transparent because of short-range ordering of the crystallins (2, 3). Mammalian lenses contain primarily a-crystallins (Mr 700,000-1,200,000), l3-crystallins (Mr 50,000-300,000) and -crystallins (Mr 20,000) (1,4,5). Their relative proportions vary with age and location within the lens as a result of both differential synthesis during development and selective degradation and insolubilization with aging (4-15). The lens nucleus is highly enriched in -crystallins, which are monomeric, basic proteins rich in sulfhydryl groups (8,(16)(17)(18)(19). The majority of human cataracts represent an irreversible opacification of the lens nucleus that progresses with age, a condition that is accompanied by oxidation of sulfhydryl groups, aggregation, and insolubilization of the various crystallins (4,8,13,(20)(21)(22)(23).The cold cataract phenomenon observed in most young mammalian lenses (e.g., calf, rat, and rabbit) is a convenient model system to study the relationship between nuclear opacification and -crystallin aggregation. A temperaturedependent reversible opacification can be induced in the nucleus of these young lenses (24)(25)(26)(27)(28). This behavior appears to be an intrinsic property of the concentrated mixture of crystallins, since it also can be induced in purified, membranefree cytoplasmic extracts of lens nucleus (27,(29)(30)(31)(32). Cold cataract has been modeled as a reversible phase-separation phenomenon (26)(27)(28)(29)(30)(31)(32). Upon lowering the temperature below a critical value Tc, the cytoplasm separates into protein-rich and protein-poor d...

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Polypeptide chain pathway in γ‐crystallin IIIb from calf lens at 3 Å resolution

Cited by 26 publications

References 10 publications

Fluorescence quenching studies of the structures of calf gamma-II, III, and IV crystallins

Fluorescence quenching studies of the structures of calf gamma-II, III, and IV crystallins

A computer graphics model of frog γ‐crystallin based on the three‐dimensional structure of calf γ‐II crystallin

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

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