We have studied the assembly and GTPase of purified FtsZ from the hyperthermophilic archaeon Methanococcus jannaschii, a structural homolog of eukaryotic tubulin, employing wild-type FtsZ, FtsZ-His 6 (histidinetagged FtsZ), and the new mutants FtsZ-W319Y and FtsZ-W319Y-His 6 , with light scattering, nucleotide analyses, electron microscopy, and image processing methods. This has revealed novel properties of FtsZ. The GTPase of archaeal FtsZ polymers is suppressed in Na ؉ -containing buffer, generating stabilized structures that require GDP addition for disassembly. FtsZ assembly is polymorphic. Archaeal FtsZ(wt) assembles into associated and isolated filaments made of two parallel protofilaments with a 43 Å longitudinal spacing between monomers, and this structure is also observed in bacterial FtsZ from Escherichia coli. The His 6 extension facilitates the artificial formation of helical tubes and sheets. FtsZ-W319Y-His 6 is an inactivated GTPase whose assembly remains regulated by GTP and Mg 2؉. It forms twodimensional crystals made of symmetrical pairs of tubulin-like protofilaments, which associate in an antiparallel array (similarly to the known Ca 2؉ -induced sheets of FtsZ-His 6 ). In contrast to the lateral interactions of microtubule protofilaments, we propose that the primary assembly product of FtsZ is the double-stranded filament, one or several of which might form the dynamic Z ring during prokaryotic cell division.Bacterial cells place at their division site a Z-ring that assembles from FtsZ at the cytosolic side of the plasma membrane and recruits the other protein components of the septation machinery. The positioning of the Z-ring is in turn determined by the self-organizing Min system (1-3). Archaeal FtsZ from Methanococcus jannaschii and eukaryotic tubulin share the same structural framework and constitute a distinct family of protofilament-forming GTPases (4, 5). The structures of bacterial FtsZs are probably similar to the archaeal protein, based on FtsZ sequence conservation. The Escherichia coli Z-ring is very dynamic, with turnover in seconds, similar to or faster than a typical mitotic spindle (6). Although the position of the Z ring was visualized by immunoelectron microscopy (7), its structure is unknown. A number of studies have shown that purified bacterial FtsZ can assemble with GTP and divalent cations forming polymers that hydrolyze the nucleotide ␤-␥ phosphate bond and disassemble upon GTP consumption (8 -13), although the mechanism linking GTP hydrolysis and exchange to the polymer dynamics (14) remains controversial (15-17). FtsZ polymers have the characteristic tubulin ϳ40 Å axial spacing between consecutive monomers (18). At pH 6 and in the presence of high Ca 2ϩ and GTP concentrations, a small proportion of archaeal FtsZ from M. jannaschii formed crystalline sheets made of symmetric protofilament pairs associated in an antiparallel arrangement, whereas most of the protein precipitated into aggregates of helical cable-like tubes. Manual fitting of the structure of GDP-bound Ft...

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Background It has been reported that clinical evaluation consistently underestimates the severity of hidradenitis suppurativa (HS). Objective To determine the usefulness of ultrasound as a diagnostic tool in HS compared with clinical examination and to assess the subsequent modification of disease management. Methods Cross‐sectional multicentre study. Severity classification and therapeutic approach according to clinical vs. ultrasound examination were compared. Results Of 143 HS patients were included. Clinical examination scored 38, 70 and 35 patients as Hurley stage I, II and III, respectively; with ultrasound examination, 21, 80 and 42 patients were staged with Hurley stage I, II and III disease, respectively (P < 0.01). In patients with stage I classification as determined by clinical examination, 44.7% changed to a more severe stage. Clinical examination indicated that 44.1%, 54.5% and 1.4% of patients would maintain, increase or decrease treatment, respectively. For ultrasound examination, these percentages were 31.5%, 67.1% and 1.4% (P < 0.01). Concordance between clinical and ultrasound intra‐rater examination was 22.8% (P < 0.01); intra‐rater and inter‐rater (radiologist) ultrasound agreement was 94.9% and 81.7%, respectively (P < 0.01). Limitations The inability to detect lesions that measure ≤0.1 mm or with only epidermal location. Conclusion Ultrasound can modify the clinical staging and therapeutic management in HS by detecting subclinical disease.