On the interpretation and prediction of X‐ray scattering profiles of biomolecules in solution

Pickover, Clifford A.; Engelman, Donald M.

doi:10.1002/bip.360210408

Cited by 42 publications

(19 citation statements)

References 29 publications

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“…X-ray solution scattering profiles extending beyond the Guinier region contain information regarding the shape and internal structure of proteins (27). The solution scattering profile of Ca2+-calmodulin gave two broad maxima in the Q region between 0.25 A-' and 0.65 A-, which is expected from predictions based on the crystal structure.…”

Section: Discussionmentioning

confidence: 49%

Melittin binding causes a large calcium-dependent conformational change in calmodulin.

Kataoka

Head

Seaton

et al. 1989

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

142

116

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The interaction between calmodulin and its target protein is a key step in many calcium-regulated cellular functions. Melittin binds tightly to calmoduiln in the presence of calcium and is a competitive inhibitor of codulin function. Using melittin as a model for the target peptide of calmodulin, we have found a large Ca2+-dependent conformational change of almoulin in solution induced by peptide binding. Mg+ does not substitute for Ca2+ in producing the conformation change. Small-angle x-ray scattering has shown that calmodulin exists as a dumbbell in solution, simllar to that observed in the crystalline state. Our present measurements reveal that the overall structure of the Ca2+-calmodulinmelittin complex is not a dumbbell but a globular shape. Upon binding melittin, the radius of gyration decreases from 20.9 to 18.0 A and the largest dimension decreases from 60 to 47.5 A.In the absence of calcium, however, melittin has little effect on the solution structure of calmodulin. Because of the importance of calmodulin-enzyme interactions, much work has focused on the molecular mechanisms underlying the protein-protein interaction and the ensuing enzyme activation. The crystal structure of calmodulin (2-4) has provided the structural framework for numerous studies.In crystals, calmodulin and its close homologue troponin C adopt an unusual dumbbell shape (2-6). The two lobes of the dumbbell are connected by a central helix. Because of its unusual shape and high surface/volume ratio, this structure has raised many questions related to the form and function of the protein, including the relationship between the crystal and solution structures and the possibility of alternative conformations. Some ofthese questions have been addressed through techniques such as small-angle x-ray scattering (7,8). From small-angle x-ray scattering data, information about molecular size and shape can be obtained from protein molecules in solution, thus providing complementary data to those obtained from crystallographic methods. While small-angle x-ray scattering is a much lower resolution technique than x-ray crystallography, a major advantage, in addition to the ability to measure proteins in solution, is that samples can be studied under near-physiological conditions, which is frequently impossible for protein crystals.Differences between solution and crystal structures of calmodulin seem most likely to involve dynamic aspects of the spatial relationship of the two lobes of the molecule, governed by flexibility of the central helical region. Previous small-angle x-ray scattering studies on calmodulin (7, 8) have indicated that in solution the protein possesses an elongated bibbed shape, generally consistent with the crystal structure. However, such measurements provide information only on the time-averaged structure and do not preclude the possibility that flexibility in the helix may exist. The consequences of such flexibility, particularly in terms of its role in the interactions of calmodulin with its target proteins, have ...

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Section: Discussionmentioning

confidence: 49%

Melittin binding causes a large calcium-dependent conformational change in calmodulin.

Kataoka

Head

Seaton

et al. 1989

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

142

116

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“…Several theoretical works have been performed in order to calculate P(q) for low molecular weight proteins. 9,10 In our work, we used the CRYSOL program to calculate P(q). 10 This program calculates the form factor for macromolecules of a known atomic structure.…”

Section: Methodsmentioning

confidence: 99%

Effects of tetramethylurea on the tertiary structure of lysozyme in water

Castelletto

Arêas

et al. 1998

The Journal of Chemical Physics

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We studied by small angle x-ray scattering (SAXS) the tetramethylurea (TMU) effects on the tertiary structure of lysozyme in water. Samples containing TMU with mass fractions, w, ranging from 0 to 0.7 were analyzed. The SAXS results clearly demonstrate a structural transition from a spheroidal molecule (0⩽w⩽0.6) to a highly anisometric molecule for w=0.7. Additional SAXS results for samples with w=0.7, from which the TMU was removed, showed that this transition is reversible. The variation of the maximum dimension of the molecule with w fits an equation corresponding to a “two-state” model. At w=0.6 (critical fraction) a mixture of folded (spheroidal) and unfolded (anisometric) molecules coexists in the solution.

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“…To illustrate the use of CRYSOL, we present the results obtained for hen egg white lysozyme (molecular weight 14 KDa), which has already been used for illustrative purposes by various authors (Pickover & Engelman, 1982;Pavlov & Fedorov, 1983;Lattman, 1989). The X-ray scattering curve from a lysozyme solution (Fig.…”

Section: Examples Of Applicationsmentioning

confidence: 99%

CRYSOL– a Program to Evaluate X-ray Solution Scattering of Biological Macromolecules from Atomic Coordinates

Svergun¹,

Barberato²,

Koch³

1995

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A program for evaluating the solution scattering from macromolecules with known atomic structure is presented. The program uses multipole expansion for fast calculation of the spherically averaged scattering pattern and takes into account the hydration shell. Given the atomic coordinates (e.g. from the Brookhaven Protein Data Bank) it can either predict the solution scattering curve or fit the experimental scattering curve using only two free parameters, the average displaced solvent volume per atomic group and the contrast of the hydration layer. The program runs on IBM PCs and on the major UNIX platforms. Journal of Applied CrystallographyISSN0021-8898 © 1995

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On the interpretation and prediction of X‐ray scattering profiles of biomolecules in solution

Cited by 42 publications

References 29 publications

Melittin binding causes a large calcium-dependent conformational change in calmodulin.

Melittin binding causes a large calcium-dependent conformational change in calmodulin.

Effects of tetramethylurea on the tertiary structure of lysozyme in water

CRYSOL– a Program to Evaluate X-ray Solution Scattering of Biological Macromolecules from Atomic Coordinates

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