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PubMed1990

Evidence that conserved residues Cys-62 and Cys-154 within the Azotobacter vinelandii nitrogenase MoFe protein alpha-subunit are essential for nitrogenase activity but conserved residues His-83 and Cys-88 are not.

Metallocluster extrusion requirements, interspecies MoFe-protein primary sequence comparisons and comparison of the primary sequences of the MoFe-protein subunits with each other have been used to assign potential P-cluster (Fe-S cluster) domains within the MoFe protein. In each alpha-beta unit of the MoFe protein, alpha-subunit domains, which include potential Fe-S cluster ligands Cys-62, His-83, Cys-88 and Cys-154, and beta-subunit domains, which include potential Fe-S cluster ligands Cys-70, His-90, Cys-95 and Cys-153, are proposed to comprise nearly equivalent P-cluster environments located adjacent to each other in the native protein. As an approach to test this model and to probe the functional properties of the P clusters, amino acid residue substitutions were placed at the alpha-subunit Cys-62, His-83, Cys-88 and Cys-154 positions by site-directed mutagenesis of the Azotobacter vinelandii nifD gene. The diazotrophic growth rates, MoFe-protein acetylene-reduction activities, and whole-cell S = 3/2 electron paramagnetic resonance spectra of these mutants were examined. Results of these experiments show that MoFe-protein alpha-subunit residues, Cys-62 and Cys-154, are probably essential for MoFe-protein activity but that His-83 and Cys-88 residues are not. These results indicate either that His-83 and Cys-88 do not provide essential P-cluster ligands or that a new cluster-ligand arrangement is formed in their absence.

Amino Acid Sequence↗
PubMedDate not supplied

Conservative total hip arthroplasty: a procedure to conserve bone stock. Part I: analysis of sixty-six patients. Part II: analysis of failures.

Pain relief, function, and range of motion in surface replacement hip arthroplasty is comparable to the Charnley-type conventional arthroplasty. Patients with primary and secondary degenerative hip disease are the most suitable candidates for surface replacement. Previous operations, especially mold arthroplasty, increases incidence of failure. Osteopenia, obesity, or congenital deficiency of the acetabulum also increases the incidence of failure. Intraoperative preservation of abductor continuity and rigorous postoperative abductor strengthening are necessary to insure the success of the procedure. A minimum of 18 months is necessary to adequately evaluate the procedure. Acetabular loosening is avoidable. Hemispherical reaming of the femoral head did not contribute to femoral component loosening. Traumatic femoral neck fracture is a concern, but atraumatic femoral neck fracture can be avoided through improved operative technique, and by a program of rehabilitation of hip musculature. The procedure is indicated in the relatively young, well-motivated, non-obese patient with degenerative joint disease who has normal hip musculature.

Acetabulum↗
PubMedDate not supplied

[Conservative treatment of splenic injuries in adults. Conservation or surgery?].

A preservative attitude towards splenic traumatism is globally no more discussed. But the best way to succeed for the general surgeon has to be precise: non operative either coeliotomy for preservative surgery? About 55 observations of splenic traumatisms, the authors compare advantages with drawback of each position and try to show out the factors acting on each choice to aim a preservative score the highest possible. Now the global preservative score is 47%. The non operative proceeding lead 5/12 to failure. 10 preservative surgery initially performed lead to 10 success: preservative surgery, in our hands give the best results. Preservative surgery for a greater number of cases, and mainly for polytraumatisms (or multiple contusions) for which the collaboration of surgeons from different specialties make more difficult, for more stratified, the supervision in case of non operative proceeding.

Abdominal Injuries↗