2 research outputs found
Determining crystal structures through crowdsourcing and coursework
We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality
Chemoenzymatic Total Synthesis and Structural Diversification of Tylactone-Based Macrolide Antibiotics through Late-Stage Polyketide Assembly, Tailoring, and Cî—¸H Functionalization
Polyketide synthases
(PKSs) represent a powerful catalytic platform
capable of effecting multiple carbon–carbon bond forming reactions
and oxidation state adjustments. We explored the functionality of
two terminal PKS modules that produce the 16-membered tylosin macrocycle,
using them as biocatalysts in the chemoenzymatic synthesis of tylactone
and its subsequent elaboration to complete the first total synthesis
of the juvenimicin, M-4365, and rosamicin classes of macrolide antibiotics
via late-stage diversification. Synthetic chemistry was employed to
generate the tylactone hexaketide chain elongation intermediate that
was accepted by the juvenimicin (Juv) ketosynthase of the penultimate
JuvEIV PKS module. The hexaketide is processed through two complete
modules (JuvEIV and JuvEV) in vitro, which catalyze elongation and
functionalization of two ketide units followed by cyclization of the
resulting octaketide into tylactone. After macrolactonization, a combination
of in vivo glycosylation, selective in vitro cytochrome P450-mediated
oxidation, and chemical oxidation was used to complete the scalable
construction of a series of macrolide natural products in as few as
15 linear steps (21 total) with an overall yield of 4.6%