Tag: Compound

X-Rays Shed Light on Possible New Treatments for TB

X-Rays Shed Light on Possible New Treatments for TB

SCIENTIFIC ACHIEVEMENT

X-ray diffraction data, collected at the Advanced Light Source (ALS) and other Department of Energy light sources, revealed the crystal structure of CMX410, a new compound that targets a key enzyme (Pks13) in the cell membrane of the bacterium responsible for tuberculosis (TB).

SIGNIFICANCE AND IMPACT

CMX410 is a promising new candidate to treat TB, including multidrug-resistant strains.

New treatments needed to tackle an old foe

TB is a deadly infectious disease caused by the bacterium Mycobacterium tuberculosis (Mtb). According to the World Health Organization, an estimated 10.8 million people contracted TB globally in 2023, and 1.25 million died from the disease. While antibiotics are effective for drug-sensitive TB cases, multidrug-resistant Mtb strains can evade common drug therapies.

Drug-resistant cases require a regimen that is often more expensive, toxic, and time-intensive. Patients are required to take six or more medications daily for up to 20 months. New approaches are urgently needed to shorten the course of drug interventions and address widespread multidrug-resistant strains.

A multi-institutional study led by researchers at Texas A&M University and the Calibr-Skaggs Institute for Innovative Medicine sought to find new treatments to address multidrug-resistant TB. The team screened a library of 406 compounds that belong to an active class of molecules [i.e., sulfur fluoride exchange (SuFEx)] to evaluate their efficacy against Mtb. The team developed one promising compound into CMX410, which targets Pks13, an enzyme essential for microbial cell wall biosynthesis.

Read more on the ALS website

Image: A cross-section of the crystal structure for the enzyme Pks13 (the surface colored pink and blue by hydrophobicity) as it interacts with CMX410 (shown as stick-like structure), a new drug candidate for TB

Credit: ALS

A promising compound for reversible male contraception

A promising compound for reversible male contraception

Researchers found that a small-molecule protein inhibitor—screened from billions of compounds and analyzed using structural insights from protein crystallography performed at the Advanced Light Source (ALS)—reversibly suppresses male fertility in mice.

The work addresses the pressing need for more contraceptive options that enable all individuals to control their own fertility.

Eight billion and counting

The United Nations designated November 15, 2022, as the Day of Eight Billion, the day the population of our planet passed eight billion people. This number is projected to reach ten billion by 2050. A sobering statistic is that nearly half of all pregnancies worldwide are unintended, which results in emotional, physical, and financial burdens on individuals as well as health care systems.

Contraception enables individuals to choose when and whether to conceive. But more options are needed—for nonhormonal contraceptives (which target specific proteins related to reproduction) and for non-barrier, reversible methods for men.

Here, researchers identified a molecule that blocks an enzyme key to male fertility. Using protein crystallography, they gained valuable structure–activity insight and, in tests on mice, showed that an optimized version of the compound is both effective and reversible.

Shining light on a “dark kinase”

The protein target in this work is an enzyme called serine/threonine kinase 33 (STK33). Kinases activate cellular processes and are therefore prime targets for drug therapies. However, there are over 500 human kinases, and many—sometimes called “dark kinases”—are under-researched and poorly understood. STK33 fell into this category, until a study of men with STK33 mutations and experiments in which the STK33 gene was nullified in mice established that deactivating STK33 in males suppresses fertility.

To identify small-molecule drug candidates for blocking STK33, the researchers used a high-throughput screening process whereby each candidate molecule was tagged with a unique DNA sequence. This enabled the screening of billions of molecules together with STK33 in a single test tube. Compounds that ended up tightly bound to the protein (“hits”) could then be identified by sequencing the DNA tags.

Structure-guided design

To understand the molecular basis for high-affinity STK33 inhibitors, the researchers used protein crystallography at ALS Beamline 5.0.2 to determine the structure of STK33, co-crystallized with a hit from the screening process (CDD-2211) that proved amenable to crystallization.

Because the structure of STK33 had never been previously determined, the researchers were surprised to discover that it formed a dimer. The data also settled the question of how molecules are oriented in the binding pocket, after predictive models had given two different possibilities. Specific interactions between the molecule and the protein’s amino acids showed why CD-2211 has such high affinity for STK33. This information will prove very useful in tailoring compounds for greater STK33 specificity.

Read more on ALS website

Image: Surface view of a protein (STK33) that, when inhibited, produces contraceptive effects. A small-molecule inhibitor is shown as a stick model (yellow=carbon, red=oxygen, and blue=nitrogen) in the protein’s binding pocket.