(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Bacteria: NE > Terrabacteria group: NE > Actinobacteria [phylum]: NE > Actinobacteria [class]: NE > Streptomycetales: NE > Streptomycetaceae: NE > Streptomyces: NE > Streptomyces parvulus: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MTGTNTHSDVWIRQYRPAHPTAPQLICLPHAGGSATFYHPVAAALAPRCD VLAVQYPGRQDRRAEKPLEDIDELANQLFPVLRARVHQPVALFGHSMGAT LAFELARRFESAGISLEALLVSARPAPSRQRTGGTVHLLSDEELVAELRT LDGTAEQVFHDEELVRMALPAIRGDYRAAETYRYRPGPKLRCPIHALTGD DDPMVTPVEARAWSEHTDGPFTLDTFAGGHFYLLEHRDAILGIIAEHLRT CSRAPGDRSGLTRE
alpha/beta hydrolases make up a large and diverse protein superfamily. In natural product biosynthesis, cis-acting thioesterase alpha/beta hydrolases can terminate biosynthetic assembly lines and release products by hydrolyzing or cyclizing the biosynthetic intermediate. Thioesterases can also act in trans, removing aberrant intermediates and restarting stalled biosynthesis. Knockout of this "editing" function leads to reduced product titers. The borrelidin biosynthetic gene cluster from Streptomyces parvulus Tu4055 contains a hitherto uncharacterized stand-alone thioesterase, borB. In this work, we demonstrate that purified BorB cleaves acyl substrates with a preference for propionate, which supports the hypothesis that it is also an editing thioesterase. The crystal structure of BorB shows a wedgelike hydrophobic substrate binding crevice that limits substrate length. To investigate the structure-function relationship, we made chimeric BorB variants using loop regions from characterized homologues with different specificities. BorB chimeras slightly reduced activity, arguing that the modified region is a not major determinant of substrate preference. The structure-function relationships described here contribute to the process of elimination for understanding thioesterase specificity and, ultimately, engineering and applying trans-acting thioesterases in biosynthetic assembly lines.
The biosynthetic gene cluster for the angiogenesis inhibitor borrelidin has been cloned from Streptomyces parvulus Tu4055. Sequence analysis indicates that the macrolide ring of borrelidin is formed by a modular polyketide synthase (PKS) (borA1-A6), a result that was confirmed by disruption of borA3. The borrelidin PKS is striking because only seven rather than the nine modules expected for a nonaketide product are encoded by borA1-A6. The starter unit of the PKS has been verified as trans-cyclopentane-1,2-dicarboxylic acid (trans-1,2-CPDA), and the genes involved in its biosynthesis identified. Other genes responsible for biosynthesis of the nitrile moiety, regulation, and self-resistance were also identified.
Streptomyces parvulus thioesterase type II, BorB from the borrelidin biosynthetic gene cluster
