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The Switch I and II Regions of MinD Are Required for Binding and Activating MinC. Huaijin Zhou, 2004.MinD and MinC cooperate to form an efficient inhibitor of Z-ring formation that is spatially regulated by MinE . MinD activatesMinC by recruiting it to the membrane and targeting it to aseptal component . To better understand this activation, we haveisolated loss-of-function mutations in minD and carried out site-directed mutagenesis . Many of these mutations block MinC-MinD interaction; however, they also prevent MinD self-interactionand membrane binding, suggesting that they affect nucleotideinteraction or protein folding . Two mutations in the switchI region [MinD box] and one mutation in the switch II regionhad little affect on most MinD functions, such as MinD self-interaction,membrane binding, and MinE stimulation; however, they did eliminateMinD-MinC interaction . Two additional mutations in the switchII region did not affect MinC binding . Further study revealedthat one of these allowed the MinCD complex to target to theseptum but was still deficient in blocking division . These resultsindicate that the switch I and II regions of MinD are requiredfor interaction with MinC but not MinE and that the switch IIregion has a role in activating MinC. Molecular and Biological Characterization of a Cryptosporidium molnari-Like Isolate from a Guppy (Poecilia reticulata). Una Ryan, 2004.Histological, morphological, genetic, and phylogenetic analyses of a Cryptosporidium molnari-like isolate from a guppy (Poecilia reticulata) identified stages consistent with those of C . molnari and revealed that C . molnari is genetically very distinct from all other species of Cryptosporidium . This study represents the first genetic characterization of C . molnari . Transcription Analysis of the Bacillus subtilis PucR Regulon and Identification of a cis-Acting Sequence Required for PucR-Regulated Expression of Genes Involved in Purine Catabolism. Lars Beier, 2002.The PucR protein of Bacillus subtilis has previously been suggested to regulate the expression of 15 genes, pucABCDE, pucFG, pucH, pucI, pucJKLM, pucR, and gde, all of which encode proteins involved in purine catabolism . When cells are grown under nitrogen-limiting conditions, the expression of these genes is induced and intermediary compounds of the purine catabolic pathway affect this expression . By using pucR deletion mutants, we have found that PucR induces the expression of pucFG, pucH, pucI, pucJKLM, and gde while it represses the expression of pucR and pucABCDE . Deletions in the promoters of the five induced operons and genes combined with bioinformatic analysis suggested a conserved upstream activating sequence, 5'-WWWCNTTGGTTAA-3', now named the PucR box . Potential PucR boxes overlapping the -35 and -10 regions of the pucABCDE promoter and located downstream of the pucR transcription start point were also found . The positions of these PucR boxes are consistent with PucR acting as a negative regulator of pucABCDE and pucR expression . Site-directed mutations in the PucR box upstream of pucH and pucI identified positions that are essential for the induction of pucH and pucI expression, respectively . Mutants with decreased pucH or increased pucR expression obtained from a library of clones containing random mutations in the pucH-to-pucR intercistronic region all contained mutations in or near the PucR box . The induction of pucR expression under nitrogen-limiting conditions was found to be mediated by the global nitrogen-regulatory protein TnrA . In other gram-positive bacteria, we have found open reading frames that encode proteins similar to PucR located next to other open reading frames encoding proteins with similarity to purine catabolic enzymes . Hence, the PucR homologues are likely to exert the same function in other gram-positive bacteria as PucR does in B . subtilis .
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