A xenon-filled multiwire arc detector for X-ray diffraction

Cork, C.; Hamlin, R.; Vernon, W.; Xuong, N.-H.

doi:10.1107/s0567739475001490

Cited by 24 publications

(9 citation statements)

References 4 publications

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“…radiation from an Elliot GX21 generator. X-ray intensity data were collected on a multiwire area detector of the type developed by Cork et al (12). An initial 5-A-resolution data set was collected from one crystal for the Patterson search study described in this paper.…”

Section: Methodsmentioning

confidence: 99%

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Allen¹,

Fehér²,

Yeates³

et al. 1986

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

347

165

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Crystals of the reaction center (RC) from RCs from purple photosynthetic bacteria contain three subunits, L, M, and H (present in a 1:1:1 stoichiometry) and a number of cofactors: four bacteriochlorophylls (BChls), two bacteriopheophytins, two quinones, QA (primary electron acceptor), and QB (secondary electron acceptor), and one nonheme iron (for reviews, see refs. 1 and 2). Although RCs from different species exhibit many similarities in structure, there are some significant structural differences.The RCs from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis that are the subject of this investigation show the following differences. In R. sphaeroides the secondary, water-soluble cytochrome is not present in purified RCs. In contrast, RCs from R. viridis contain a fourth subunit, a cytochrome, that has four heme groups associated with it. The two species contain different types of BChl: R. sphaeroides has BChl-a whereas R. viridis contains BChl-b. The primary quinone in R. sphaeroides is a ubiquinone, whereas in R. viridis it is a menaquinone. Furthermore, the two quinones that serve as acceptors are retained in purified RCs from R. sphaeroides, but one is apparently lost from R. viridis during the purification.Although extensive work has been done during the past two decades to characterize RCs, until recently there was very little information available on their three-dimensional structure. The reason was the lack of crystals suitable for x-ray diffraction studies. This situation changed with the successful crystallization of RCs from R. viridis (3) and R. sphaeroides (4, §). These crystals are of sufficient size and quality to obtain good x-ray diffraction data. The structure of the RCs from R. viridis has been reported recently at a resolution of 3 A (5, 6).In this work we describe the use of the Patterson search (molecular replacement) method (for reviews, see refs. 7 and 8) to obtain a low-resolution electron density map of the RC from R. sphaeroides and to show the homology between the structures of the RCs from the two bacterial species. A preliminary account of this work has been presented (9).EXPERIMENTAL PROCEDURES Crystallization. The RC from R. sphaeroides was crystallized by using the vapor diffusion technique. Different crystallization conditions produced a variety of forms as reported (4,10,11). The crystal form used for these structural studies was grown under the following conditions. The initial protein solution consisted of 5 mg of RC per ml, 0.36 M NaCl, 3.9%

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Section: Methodsmentioning

confidence: 99%

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Allen¹,

Fehér²,

Yeates³

et al. 1986

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

347

165

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“…X-ray diffraction intensities were obtained by using a newly developed multiwire area detector diffractometer (13). This technique permitted very rapid collection of data and made possible extensive replication to a resolution of 2.5 A with only one crystal each of the parent and the heavy-atom derivatives.…”

mentioning

confidence: 99%

Dihydrofolate Reductase: X-ray Structure of the Binary Complex with Methotrexate

Matthews

Alden

Bolin

et al. 1977

Science

Self Cite

343

206

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A central eight-stranded beta-pleated sheet is the main feature of the polypeptide backbone folding in dihydrofolate reductase. The innermost four strands and two bridging helices are geometrically similar to but are connected in a different way from those in the dinucleotide binding domains found in nicotinamide-adenine dinucleotide-linked dehydrogenases. Methotrexate is bound in a 15-angstrom-deep cavity with the pteridine ring buried in a primarily hydrophobic pocket, although a strong interaction occurs between the side chain of aspartic acid 27 and N(1), N(8), and the 2-amino group of methotrexate.

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“…One multiwire proportional counter (Cork et al, 1975;Xuong et al, 1985) was used and CuK,, radiation was obtained with a graphite monochromater.…”

Section: X-ray Data Collectionmentioning

confidence: 99%

Kinetics and crystal structure of a mutant Escherichia coli alkaline phosphatase (Asp‐369 → Asn): A mechanism involving one zinc per active site

Tibbitts

Kantrowitz

1994

Protein Science

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Using site-directed mutagenesis, an aspartate side chain involved in binding metal ions in the active site of Escherichia coli alkaline phosphatase (Asp-369) was replaced, alternately, by asparagine (D369N) and by alanine (D369A). The purified mutant enzymes showed reduced turnover rates ( kcat) and increased Michaelis constants ( K , ) . The kc,, for the D369A enzyme was 5,000-fold lower than the value for the wild-type enzyme. The D369N enzyme required Zn2+ in millimolar concentrations to become fully active; even under these conditions the kc,, measured for hydrolysis of p-nitrophenol phosphate was 2 orders of magnitude lower than for the wild-type enzyme. Thus the k,,/Km ratios showed that catalysis is 50 times less efficient when the carboxylate side chain of Asp-369 is replaced by the corresponding amide; and activity is reduced to near nonenzymic levels when the carboxylate is replaced by a methyl group. The crystal structure of D369N, solved to 2.5 A resolution with an R-factor of 0.189, showed vacancies at 2 of the 3 metal binding sites. On the basis of the kinetic results and the refined X-ray coordinates, a reaction mechanism is proposed for phosphate ester hydrolysis by the D369N enzyme involving only 1 metal with the possible assistance of a histidine side chain.

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A xenon-filled multiwire arc detector for X-ray diffraction

Cited by 24 publications

References 4 publications

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Structural homology of reaction centers from Rhodopseudomonas sphaeroides and Rhodopseudomonas viridis as determined by x-ray diffraction.

Dihydrofolate Reductase: X-ray Structure of the Binary Complex with Methotrexate

Kinetics and crystal structure of a mutant Escherichia coli alkaline phosphatase (Asp‐369 → Asn): A mechanism involving one zinc per active site

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