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C H Weber

Publications and source records attributed to C H Weber.

At least 19 recordsLinked to original sources
PubMed1999

Refined structures of oxidized flavodoxin from Anacystis nidulans.

Flavodoxin from Anacystis nidulans (Synechococcus PCC 7942) was the first member of the flavodoxin family to be characterized, and is the structural prototype for the "long-chain" flavodoxins that have molecular masses of approximately 20 kDa. Crystal structure analyses and refinements of three orthorhombic forms of oxidized A. nidulans flavodoxin are reported, and salient features of the fold and the FMN binding site are compared with other flavodoxins. The structure of form I (wild-type: P212121, a=57.08 A, b=69.24 A, c=45.55 A), determined initially by multiple isomorphous replacement, has been refined to R=0.183 and R(free)=0.211 for data from 10.0 to 1.7 A resolution. Structures of form II (wild-type: P212121, a=60.05 A, b=65.85 A, c=51.36 A) and form III (Asn58Gly: P212121, a=51.30 A, b=59.15 A, c=94.44 A) have been determined by molecular replacement and refined versus data to 2.0 A and 1.85 A, respectively; the R values for forms II and III are 0.147 and 0.150. Changes in the molecular contacts that produce the alternative packings in these crystalline forms are analyzed. Deletion of the Asn side-chain in the mutant Asn58Gly removes an intermolecular stacking interaction and allows the alternative packing found in form III crystals. The functionally important 50's loop of the FMN binding site is less restrained by intermolecular contacts in these crystals but maintains the same conformation as in oxidized wild type protein. The structures reported here provide the starting point for structure-function studies of the reduced states and of mutants, described in the accompanying paper.

Amino Acid Sequence↗
PubMed1999

Comparisons of wild-type and mutant flavodoxins from Anacystis nidulans. Structural determinants of the redox potentials.

The long-chain flavodoxins, with 169-176 residues, display oxidation-reduction potentials at pH 7 that vary from -50 to -260 mV for the oxidized/semiquinone (ox/sq) equilibrium and are -400 mV or lower for the semiquinone/hydroquinone (sq/hq) equilibrium. To examine the effects of protein interactions and conformation changes on FMN potentials in the long-chain flavodoxin from Anacystis nidulans (Synechococcus PCC 7942), we have determined crystal structures for the semiquinone and hydroquinone forms of the wild-type protein and for the mutant Asn58Gly, and have measured redox potentials and FMN association constants. A peptide near the flavin ring, Asn58-Val59, reorients when the FMN is reduced to the semiquinone form and adopts a conformation ("O-up") in which O 58 hydrogen bonds to the flavin N(5)H; this rearrangement is analogous to changes observed in the flavodoxins from Clostridium beijerinckii and Desulfovibrio vulgaris. On further reduction to the hydroquinone state, the Asn58-Val59 peptide in crystalline wild-type A. nidulans flavodoxin rotates away from the flavin to the "O-down" position characteristic of the oxidized structure. This reversion to the conformation found in the oxidized state is unusual and has not been observed in other flavodoxins. The Asn58Gly mutation, at the site which undergoes conformation changes when FMN is reduced, was expected to stabilize the O-up conformation found in the semiquinone oxidation state. This mutation raises the ox/sq potential by 46 mV to -175 mV and lowers the sq/hq potential by 26 mV to -468 mV. In the hydroquinone form of the Asn58Gly mutant the C-O 58 remains up and hydrogen bonded to N(5)H, as in the fully reduced flavodoxins from C. beijerinckii and D. vulgaris. The redox and structural properties of A. nidulans flavodoxin and the Asn58Gly mutant confirm the importance of interactions made by N(5) or N(5)H in determining potentials, and are consistent with earlier conclusions that conformational energies contribute to the observed potentials.The mutations Asp90Asn and Asp100Asn were designed to probe the effects of electrostatic interactions on the potentials of protein-bound flavin. Replacement of acidic by neutral residues at positions 90 and 100 does not perturb the structure, but has a substantial effect on the sq/hq equilibrium. This potential is increased by 25-41 mV, showing that electrostatic interaction between acidic residues and the flavin decreases the potential for conversion of the neutral semiquinone to the anionic hydroquinone. The potentials and the effects of mutations in A. nidulans flavodoxin are rationalized using a thermodynamic scheme developed for C. beijerinckii flavodoxin.

Amino Acid Sequence↗
PubMed1999

A prototypical cytidylyltransferase: CTP:glycerol-3-phosphate cytidylyltransferase from bacillus subtilis.

BACKGROUND: The formation of critical intermediates in the biosynthesis of lipids and complex carbohydrates is carried out by cytidylyltransferases, which utilize CTP to form activated CDP-alcohols or CMP-acid sugars plus inorganic pyrophosphate. Several cytidylyltransferases are related and constitute a conserved family of enzymes. The eukaryotic members of the family are complex enzymes with multiple regulatory regions or repeated catalytic domains, whereas the bacterial enzyme, CTP:glycerol-3-phosphate cytidylyltransferase (GCT), contains only the catalytic domain. Thus, GCT provides an excellent model for the study of catalysis by the eukaryotic cytidylyltransferases. RESULTS: The crystal structure of GCT from Bacillus subtilis has been determined by multiwavelength anomalous diffraction using a mercury derivative and refined to 2.0 A resolution (R(factor) 0.196; R(free) 0.255). GCT is a homodimer; each monomer comprises an alpha/beta fold with a central 3-2-1-4-5 parallel beta sheet. Additional helices and loops extending from the alpha/beta core form a bowl that binds substrates. CTP, bound at each active site of the homodimer, interacts with the conserved (14)HXGH and (113)RTXGISTT motifs. The dimer interface incorporates part of a third motif, (63)RYVDEVI, and includes hydrophobic residues adjoining the HXGH sequence. CONCLUSIONS: Structure superpositions relate GCT to the catalytic domains from class I aminoacyl-tRNA synthetases, and thus expand the tRNA synthetase family of folds to include the catalytic domains of the family of cytidylyltransferases. GCT and aminoacyl-tRNA synthetases catalyze analogous reactions, bind nucleotides in similar U-shaped conformations, and depend on histidines from analogous HXGH motifs for activity. The structural and other similarities support proposals that GCT, like the synthetases, catalyzes nucleotidyl transfer by stabilizing a pentavalent transition state at the alpha-phosphate of CTP.

Amino Acid Sequence↗
PubMed1998

Agarose-embedded tissue arrays for histologic and genetic analysis.

To facilitate the histologic analysis of large numbers of 7-day-old zebrafish (Danio rerio), a method has been developed to process them in agarose-embedded arrays. Using thin tissue sections, the morphology of cells and tissues can be examined microscopically to investigate a variety of biologic processes. Because of their small size, precise arrangement of the larvae is necessary to section them simultaneously. A technique was designed to embed groups of zebrafish larvae in a single plane in agarose before sectioning. Stained tissue sections of thousands of larvae can be examined efficiently using this embedding method. In addition to histologic analysis, PCR-based genotypic analysis of DNA from individual larval sections is also possible. This technique can be modified to accommodate any study that requires the histologic examination of many pieces of tissue.

Animals↗
PubMed1996

Papillary cystic and solid tumor of the pancreas.

The papillary cystic and solid tumor of the pancrease (PCSTP) is a primary pancreatic neoplasm of unknown etiology occurring most commonly in young women and regularly containing hemorrhagic areas. Clinical symptoms are non-specific. Although these tumors reach an average diameter of 10 cm, they are often discovered by accident. Because patients with surgically resected PCSTP have very good prognoses, it is important to distinguish these tumors from other growths in the pancreas, for example mucinous cystadenoma. Whereas, due to the variable proportion of fluid components, these tumors offer non-characteristic structure at ultrasonography, computed tomography (CT) possesses high specificity for PCSTP, particularly when calcifications are present. Angiography distinguishes these tumors from hypervascular neoplasms, such as the endocrinologically inactive islet cell tumor. Magnetic resonance tomography (MRT) is especially suited for imaging the hemorrhagic areas in solid tumor formations, as well as hemorrhagic debris in the fluid portions and layer phenomena are frequently observed.

Adult↗
PubMed1993

Synthesis of normal and variant human hypoxanthine-guanine phosphoribosyltransferase in Escherichia coli.

Naturally occurring mutations in hypoxanthine-guanine phosphoribosyltransferase (HPRT) have been identified by amino acid sequencing, cDNA cloning, and direct nucleotide sequencing of PCR-amplified transcripts. To determine the effect these mutations have on the catalytic properties of the molecule, knowledge of the three-dimensional structure of HPRT is required. A prerequisite for this, however, is the availability of a large amount of purified product for crystallization and x-ray diffraction analysis. For these reasons we have developed an effective means of producing high levels of human HPRT in Escherichia coli using the expression cassette PCR. By taking advantage of a T7 polymerase/promoter system, we have expressed both normal and variant human hprt sequences in E. coli. The proteins synthesized from these sequences are immunologically and enzymatically active, and are physically indistinguishable from the HPRT in B-lymphoblasts derived from normal and three HPRT-deficient subjects.

Base Sequence↗
PubMed1993

Inferred protein content and distribution from density measurements of calcitic and aragonitic otoconia.

Otoconia from the peripheral portion of the vestibular system contain specific proteins and are mineralized by several polymorphs of calcium carbonate. To infer the internal distribution of their mineral and protein components, we have measured the densities, by equilibrium centrifugation, and the lengths of aragonitic otoconia from the African clawed frog (Xenopus laevis) and calcitic otoconia from the Norway rat (Rattus norvegicus). The densities are statistically dependent on the length of the otoconia. Further, this dependence is not the same for aragonitic and calcitic otoconia. Aragonitic otoconia are statistically more dense when smaller and less dense when larger. For calcitic otoconia the opposite is true; the smaller otoconia are statistically less dense than larger otoconia. Because the organic and inorganic phases have different densities, this indicates that the otoconial proteins and the mineral phases have different distributions within these two types of otoconia.

Animals↗
PubMed1978

Oligospermia secondary to müllerian duct cyst. Simple surgical cure.

Fertility evaluation of a twenty-three-year-old male with severe oligospermia revealed a müllerian duct cyst that appeared to compress both ejaculatory ducts. Simple endoscopic unroofing of the cyst was followed by disappearance of the mass felt rectally, improvement of the radiographic appearance of the seminal tracts, and a return of the seminal analyses to well within fertile range. Müllerian duct cysts may be a rare cause of surgically correctable male infertility. Endoscopic unroofing of small müllerian duct cysts appears to be the treatment of choice in young males in whom there is concern for preserving fertility and potency.

Adult↗
PubMed1978

Accuracy of preoperative studies in staging nonseminomatous germ cell testicular tumors.

The preoperative staging procedures used in 45 patients with surgical Stage I and Stage II nonseminomatous germ cell tumors of the testis were analyzed retrospectively. Our results indicate that gallium-67-citrate scan and supraclavicular lymph node biopsy add little information in the routine preoperative evaluation of these patients. Bipedal lymphangiography, in our experience, was no more accurate than excretory urograms in selecting patients with retroperitoneal disease and in addition provides no information regarding the status of the upper urinary tract. Thus, we suggest that physical examination, excretory urography, chest x-ray film, whole lung tomography, serum tumor markers, and liver scan provide sufficient information to proceed with surgical treatment when appropriate.

Humans↗
PubMed1978

Anorchism versus cryptorchidism: the importance of a diligent search for intra-abdominal testes.

We reviewed 13 cases of testicular tumors arising in cryptorchid, intra-abdominal testes. All types of germinal neoplasms were found, seminoma being the most common. Of the 13 patients 5 had undergone limited exploration previously, with no testis being identified and, thus, were thought to have had unilateral anorchism. The importance of a thorough exploration of the peritoneal cavity is emphasized.

Adult↗
PubMed1977

Carcinoma in the defunctionalized bladder: report of a case and review of the literature.

There are few reports in the literature of carcinoma developing in the post-diversionary bladder. The sixth such case is reported and the pertinent literature is reviewed. All cases of carcinoma in defunctionalized bladders have been associated with chronic inflammation of the bladder and all tumors became apparent within 4 years of diversion. Simple cystectomy at the time of diversion should be considered for patients with a long history of bladder inflammation.

Aged↗
PubMed1977

Segmental replacement of the ureter using Sparks' mandrils. An experimental study.

Segmental ureteral replacement with free autogenous fibroelastic Dacron tube grafts in three dogs was unsuccessful during preliminary trials. However, a proliferation of urothelium, smooth muscle, and blood vessels throughout the length of the grafts was demonstrated, providing an encouraging potential for further investigations. Technical refinements are suggested that may provide for improved success with experimental ureteral replacement.

Animals↗
PubMed1976

Chronically infected and postdiversionary bladders: cytologic and histopathologic study.

Cytologic and histopathologic study of 36 patients demonstrated an 86 to 92 per cent incidence of squamous metaplasia of the bladder among patients with chronically infected bladders and a 64 per cent incidence in patients with postdiversionary bladders left behind. The relationships of infection, inflammation, squamous meetaplasia, and squamous cell carcinoma of the bladder are reviewed. It is postulated that the same carcinogenic factors which induce transitional cell carcinoma might cause squamous cell carcinoma if the epithelium had previously undergone squamous metaplasia.

Carcinoma, Squamous Cell↗
PubMed1976

Chronic seminal vesiculosis. Distressing syndrome with surgical cure.

Six cases in which a symptom complex suggestive of chronic seminal vesicular dysfunction are described. Transvesical seminal vesiculectomy was performed with good results and no disturbance of sexual potency. Seminal vesiculectomy appears to provide a reasonable means for cure of those patients who meet the specific criteria outlined.

Adult↗
PubMed1976

Benign fibrous paratesticular tumors.

Utilizing the criteria of Goodwin, a case each of chronic proliferative periorchitis and multiple fibromas of the tunica vaginalis testis causing paratesticular tumors is presented and discussed. Both of these rate processes appear to be distinct and separate clinical entities, although they appear to be similar histologically. With increased awareness by those treating intrascrotal masses, these processes may be correctly recognized and more testes may be salvaged.

Adult↗
PubMed1976

Retroperitoneal teratoma.

Retroperitoneal teratoma is the third most common primary retroperitoneal neoplasm of childhood ranking behind neuroblastoma and nephroblastoma. Ten per cent of these tumors are malignant. Two cases of benign retroperitoneal teratoma are reported, and the first description of the angiographic appearance of such a tumor is presented.

Adolescent↗