Crystal Structure of Caryolan-1-ol Synthase, a Sesquiterpene Synthase Catalyzing an Initial Anti-Markovnikov Cyclization Reaction.

In a continuing effort to understand reaction mechanisms of terpene synthases catalyzing initial anti-Markovnikov cyclization reactions, we solved the X-ray crystal structure of (+)-caryolan-1-ol synthase (CS) from , with and without an inactive analog of the farnesyl diphosphate (FPP) substrate, 2-fluorofarnesyl diphosphate (2FFPP), bound in the active site of the enzyme. The CS-2FFPP structure was solved to 2.65 Å resolution and showed the ligand in an elongated orientation, incapable of undergoing the initial cyclization event to form a C1-C11 bond.

Understanding mechanisms of terpene synthases using substrate analogs.

Terpene synthases (TS) transform achiral prenyl substrates into elaborate hydrocarbon scaffolds with multiple stereocenters through a series of cyclization reactions and carbon skeleton rearrangements. The reactions involve high-energy carbocation intermediates that must be stabilized by the enzyme along the pathway to the desired products. A variety of substrate analogs have been used to investigate TS mechanism.

Crystal Structure of Caryolan-1-ol Synthase, a Sesquiterpene Synthase Catalyzing an Initial Anti-Markovnikov Cyclization Reaction.

In a continuing effort to understand reaction mechanisms of terpene synthases catalyzing initial anti-Markovnikov cyclization reactions, we solved the X-ray crystal structure of (+)-caryolan-1-ol synthase (CS) from , with and without an inactive analog of the FPP substrate, 2-fluorofarnesyl diphosphate (2FFPP), bound in the active site of the enzyme. The CS-2FFPP complex was solved to 2.65 Å resolution and showed the ligand in a linear, elongated orientation, incapable of undergoing the initial cyclization event to form a bond between carbons C1 and C11.

Evaluation of SARS-CoV-2 Main Protease Inhibitors Using a Novel Cell-Based Assay.

As an essential enzyme of SARS-CoV-2, main protease (M) triggers acute toxicity to its human cell host, an effect that can be alleviated by an M inhibitor. Using this toxicity alleviation, we developed an effective method that allows a bulk analysis of the cellular potency of M inhibitors. This novel assay is advantageous over an antiviral assay in providing precise cellular M inhibition information to assess an M inhibitor.

QUANTIFYING BILATERAL INFECTION PATTERNS IN THE TREMATODE ALLOGLOSSIDIUM RENALE.

Within-host distributions of parasites can have relevance to parasite competition, parasite mating, transmission, and host health. We examined the within-host distribution of the adult trematode Alloglossidium renale infecting the paired antennal glands of grass shrimp. There are 4 possible parasite distributions for infections of paired organs: random, uniform, biased aggregation to 1 particular organ (e.