Structural and spectroscopic characterization of exogenous ligand binding to isolated factor F430 and its configurational isomers

Binding of axial ligands to the nickel(II) of isolated factor F430 from the methyl reductase enzyme of Methanobacterium thermoautotrophicum is demonstrated. Evidence of bis-ligand coordination is obtained from the x-ray absorption, optical, and resonance Raman spectral characterization of F430 and its 12,13-diepimeric isomer in the presence of a large excess of cyanide, pyridine, or 1-methylimidazole. Significant broadening and 5-10-nm red shifts of the main 430-nm optical absorption band and shifts of up to 30 cm-1 for the high-frequency Raman lines are observed upon coordination of these axial ligands. The Raman spectra of native F430 and the diepimer with a particular axial ligand are nearly identical. Nickel x-ray absorption edge spectra of the diepimer in the absence and presence of these exogenous ligands are indicative of conversion from a square-planar to a tetragonally distorted octahedral geometry. Analyses of the nickel extended x-ray absorption fine structure data for the ligated diepimer complexes yield detailed structural information for these complexes. Implications of these data with respect to the enzymatic mechanism and the structure of the enzyme-bound factor are discussed.     

Plant hormone response mutants

A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone-insensitive mutant phenotypes with defects in hormone-related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper-responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems.     

Evaluation of the obstetric significance of some pelvic characters in an 18th century British sample of known parity status.

The excavations at Christ Church, Spitalfields (1984-86) produced a sample of 968 human skeletons which were interred between 1729 and 1859. Of these, 387 were recovered in association with coffin plates stating name, age at death, and date of death. There are 138 adult females in the named sample and the obstetric histories of 94 have been reconstructed from historical documentation. Such variables as birth spacing, number of children, and age at first and last births are known for the majority of this sample. Any individual about whose history there is any doubt has been excluded from the analysis. A middle-class group, they were largely of high nutritional status and, by the standards of the day, lived in sanitary and comfortable conditions. Both males and females have a mean age at death of 56 years. The presence or absence, the typology, the severity, the width and the length of the preauricular sulcus, the presence or absence and the number of pits on the dorsal aspect of the pubic body, sulci along the anterior sacrum adjacent to the auricular facet, and the extension of the pubic tubercle were evaluated in relation to the obstetric histories of these females. Statistical analysis has demonstrated a relationship between the presence of pubic tubercle extension and parity status and between the degree of extension and the number of children borne (P < .02). Statistically there is no significant relationship (P > .05) between either the preauricular sulcus or pubic pitting and parity status. Sacral scarring is significantly associated (P < .05) with parity status, but as it was evident in only eight females it has little practical application. Sample sizes are small, and it must be considered that statistical evaluation of larger samples might detect associations between variables not demonstrated here. There is no significant relationship between any of the cortical variants under consideration and age at death.     

The quantitative analysis of endogenous folate catabolites in human urine.

In man folates are catabolized and excreted as inactive cleaved degradation products, a mixture of pteridines and p-aminobenzoylglutamate (pABGlu) or its acetamido derivative (apABGlu). The daily rate of excretion represents the inescapable use of the vitamin in metabolic activity and thus has implications for determining the recommended dietary allowance for the vitamin. Furthermore, the rate of catabolism has been suggested to rise during pregnancy and in certain disease states. A method is described for the quantitative extraction and assay of the folate catabolites pABGlu and apABGlu in human urine. Aliquots of 24-h urine collections are acidified and applied to columns of Dowex 50W cation-exchange resin. The catabolites are selectively batch-eluted with increasing concentrations of HCl. The fraction containing pABGlu is diazotized and then applied to a C18 Sep Pak column for further purification and concentration. The fraction containing apABGlu was deacetylated and reapplied to the Dowex column and then treated identically to the pABGlu fraction. The methanolic concentrates of both extracts were evaporated to dryness and reconstituted with water and pABGlu was regenerated by reductive cleavage of the diazotized material with Zn/HCl. The extracts of the two catabolites were separated by reverse-phase HPLC using a Radial Pak C18 column. Recovery of isolated material was monitored by the addition of high specific activity tritiated labels of both compounds added as internal standards to all urine aliquots prior to purification and analysis.     

FGFR2 exon IIIa and IIIc mutations in Crouzon, Jackson-Weiss, and Pfeiffer syndromes: evidence for missense changes, insertions, and a deletion due to alternative RNA splicing.

Fibroblast growth factor receptor 2 (FGFR2) mutations have been associated with the craniosynostotic conditions Crouzon, Jackson-Weiss, and Pfeiffer syndromes. Previously, mutations were described in the exons IIIa and IIIc, which form the extracellular, third immunoglobulin-like domain (IgIII) and adjacent linker regions, both of which are normally involved in ligand binding. For all three conditions, mutations were found in exon IIIc. Only in Crouzon syndrome were mutations identified in exon IIIa. In this study, 39 cases with one of these three conditions were screened for exon IIIa or IIIc mutations. Eleven mutations are reported in 17 unrelated cases. Mutations in exon IIIa are identified for not only Crouzon but also Jackson-Weiss and Pfeiffer syndromes. Four mutations in either exon IIIa or exon IIIc reported only in Crouzon syndrome are present also in one of the other two syndromes. Two insertions, one in exon IIIa in a Crouzon syndrome patient and the other in exon IIIc in a Pfeiffer syndrome patient, were observed. The latter mutation has the same alternative RNA splicing effect as a reported synonymous mutation for Crouzon syndrome. A missense mutation was detected in one Pfeiffer syndrome family in which two members had craniosynostosis without limb anomalies. The inter- and intrafamilial variability in expression of FGFR2 mutations suggests that these three syndromes, presumed to be clinically distinct, are instead representative of a spectrum of related craniosynostotic and digital disorders.