The recently identified type VI secretion systems (T6SS) have a crucial function in the virulence of various proteobacteria, including the human pathogen Vibrio cholerae. T6SS are encoded by a conserved gene cluster comprising approximately 15 open reading frames, mediating the appearance of Hcp and VgrG proteins in cell culture supernatants. Here, we analysed the function of the V. cholerae T6SS member ClpV, a specialized AAA+ protein. ClpV is crucial for a functional T6SS and interacts through its N‐terminal domain with the VipA/VipB complex that is composed of two conserved and essential members of T6SS. Transferring ClpV substrate specificity to a distinct AAA+ protein involved in proteolysis caused degradation of VipA but not Hcp or VgrG2, suggesting that VipA rather than Hcp/VgrG2 functions as a primary ClpV substrate. Strikingly, VipA/VipB form tubular, cogwheel‐like structures that are converted by a threading activity of ClpV into small complexes. ClpV‐mediated remodelling of VipA/VipB tubules represents a crucial step in T6S, illuminating an unexpected role of an ATPase component in protein secretion.

No abstract

Missense mutation leading to single amino acid polymorphism (SAP) is the type of mutation most frequently related to human diseases. The Swiss-Prot protein knowledgebase records information on such mutations in various sections of a protein entry, namely in the "feature," "comment," and "reference" fields. To facilitate users in obtaining the most relevant information about each human SAP recorded in the knowledgebase, the Swiss-Prot Variant web pages were created to provide a summary of available sequence information, as well as additional structural information on each variant. In particular, the ModSNP database was set up to store information related to SAPs and to manage the modeling of SAPs onto protein structures via an automatic homology modeling pipeline. Currently, among the 16,566 human SAPs recorded in the Swiss-Prot knowledgebase (release 42.5, 21 November 2003), more than 25% have corresponding 3D-models. Of these variants, 47% are related to disease, 26% are polymorphisms, and 27% are not yet clearly classified. The ModSNP database is updated and the subsequent model construction pipeline is launched with each weekly Swiss-Prot release. Thus, the ModSNP database represents a valuable resource for the structural analysis of protein variation. The Swiss-Prot variant pages are accessible from the NiceProt view of a Swiss-Prot entry on the ExPASy server (www.expasy.org/), via a hyperlink created for the stable and unique identifier FTId of each human SAP.

The Clp protease is conserved among eubacteria and most eukaryotes, and uses ATP to drive protein substrate unfolding and translocation into a chamber of sequestered proteolytic active sites. The main constitutive Clp protease in photosynthetic organisms has evolved into a functionally essential and structurally intricate enzyme. The model Clp protease from the cyanobacterium Synechococcus consists of the HSP100 molecular chaperone ClpC and a mixed proteolytic core comprised of two distinct subunits, ClpP3 and ClpR. We have purified the ClpP3/R complex, the first for a Clp proteolytic core comprised of heterologous subunits. The ClpP3/R complex has unique functional and structural features, consisting of twin heptameric rings each with an identical ClpP3 3 ClpR 4 configuration. As predicted by its lack of an obvious catalytic triad, the ClpR subunit is shown to be proteolytically inactive. Interestingly, extensive modification to ClpR to restore proteolytic activity to this subunit showed that its presence in the core complex is not rate-limiting for the overall proteolytic activity of the ClpCP3/R protease. Altogether, the ClpP3/R complex shows remarkable similarities to the 20 S core of the proteasome, revealing a far greater degree of convergent evolution than previously thought between the development of the Clp protease in photosynthetic organisms and that of the eukaryotic 26 S proteasome.

Polymorphisms of the cytochrome P450 2D6 (CYP2D6) gene affecting enzyme activity are involved in interindividual variability in drug efficiency/ toxicity. Four phenotypic groups are found in the general population: ultra rapid (UM), extensive (EM), intermediate (IM) and poor (PM) metabolizers. The AmpliChip CYP450 test is the first genotyping array allowing simultaneous analysis of 33 CYP2D6 alleles. The main aim of this study was to evaluate the performance of this test in CYP2D6 phenotype prediction. We first verified the AmpliChip CYP450 test genotyping accuracy for five CYP2D6 alleles routinely analysed in our laboratory (alleles 3,4,5,6, Â N; n ¼ 100). Results confirmed those obtained by real-time PCR. Major improvements using the array are the detection of CYP2D6 intermediate alleles and identification of the duplicated alleles. CYP2D6 phenotype was determined by assessing urinary elimination of dextromethorphan and its metabolite dextrorphan and compared to the array prediction (n ¼ 165). Although a low sensitivity of UM prediction by genotyping was observed, phenotype prediction was optimal for PM and satisfying for EM and IM.