RESUMO
DnaD and DnaB are essential DNA-replication-initiation proteins in low-G+C content Gram-positive bacteria. Here we use sensitive Hidden Markov Model-based techniques to show that the DnaB and DnaD proteins share a common structure that is evident across all their structural domains, termed DDBH1 and DDBH2 (DnaD DnaB Homology 1 and 2). Despite strong sequence divergence, many of the DNA-binding and oligomerization properties of these domains have been conserved. Although eluding simple sequence comparisons, the DDBH2 domains share the only strong sequence motif; an extremely highly conserved YxxxIxxxW sequence that contributes to DNA binding. Sequence alignments of DnaD alone fail to identify another key part of the DNA-binding module, since it includes a poorly conserved sequence, a solvent-exposed and somewhat unstable helix and a mobile segment. We show by NMR, in vitro mutagenesis and in vivo complementation experiments that the DNA-binding module of Bacillus subtilis DnaD comprises the YxxxIxxxW motif, the unstable helix and a portion of the mobile region, the latter two being essential for viability. These structural insights lead us to a re-evaluation of the oligomerization and DNA-binding properties of the DnaD and DnaB proteins.
Assuntos
Bacillus subtilis/genética , Proteínas de Bactérias/química , Proteínas de Ligação a DNA/química , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Sequência Conservada , DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Dados de Sequência Molecular , Ressonância Magnética Nuclear Biomolecular , Ligação Proteica , Estrutura Terciária de Proteína , Homologia de Sequência de AminoácidosRESUMO
OBJECTIVES: To evaluate the clinical findings and therapeutic options following adnexal torsion. STUDY DESIGN: A retrospective series of 135 patients presenting with adnexal torsion between January 1992 and December 2001 in Sousse- Tunisia- a university teaching hospital. RESULTS: Adnexal torsion accounted for 14.8% of surgically treated adnexal tumors. Pregnancy was associated in 17% of cases and diagnosis was accurate at first clinical examination in only 57.8% of cases. Ultrasound allowed visualisation of Adnexal Diseases in all cases. Operative laparoscopy was successfully achieved in 34% of patients. Conservative management was used in 57% of the premenopausal patients. No major postoperative complication was noted. CONCLUSION: Clinicians must be aware of a possible adnexal torsion in women with acute pelvic pain. Ultrasound is a useful tool in these situations. Laparoscopy allows diagnosis and surgical management even during pregnancy.
