We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. To learn more, click here. By continuing to use our site, you accept our use of cookies. Cookie Policy.

Features Partner Sites Information LinkXpress hp
Sign In
Advertise with Us
LGC Clinical Diagnostics

Download Mobile App




A Novel Method for Stabilizing Small Alpha-Helices Will Promote Development of Protease Inhibitors

By LabMedica International staff writers
Posted on 10 Jan 2013
Print article
By establishing a new method for stabilizing the alpha-helix structure in a small peptide, researchers were able to design a highly specific inhibitor of the enzyme calpain.

Although the physiological role of calpains, a family of calcium-regulated enzymes, is only poorly understood, they have been shown to be active participants in processes such as cell mobility and cell cycle progression, as well as cell-type specific functions such as long-term potentiation in neurons and cell fusion in myoblasts. Other reported roles of calpains are in cell function, helping to regulate clotting and the diameter of blood vessels, and playing a role in memory. Calpains have been implicated in apoptotic cell death, and appear to be an essential component of necrosis. Calpain is also involved in skeletal muscle protein breakdown due to exercise and altered nutritional states. Overexpression of calpain has been implicated as a factor in muscular dystrophy, AIDS, Alzheimer's disease, multiple sclerosis, and cancer.

Investigators at the University of Pennsylvania (Philadelphia, USA) and collaborators at the University of California, San Francisco (USA) and Queen's University (Ontario, Canada) screened 24 commercially available cross-linking reagents before succeeding to stabilize the alpha-helix at the center of the binding site between calpain and its natural inhibitor calpastatin.

Calpastatin consists of an N-terminal domain and four repetitive calpain-inhibition domains and is involved in the proteolysis of amyloid precursor protein. The calpain/calpastatin system is involved in numerous membrane fusion events, such as neural vesicle exocytosis and platelet and red cell aggregation. The encoded protein is also thought to affect the expression levels of genes encoding structural or regulatory proteins.

The investigators examined the effects of cross-linking on the alpha-helicity of selected peptides by CD (circular dichroism) and NMR (nuclear magnetic resonance) spectroscopy and found that structurally rigid cross-linkers were best for stabilizing alpha-helices. They reported in the October 24, 2012, issue of the Journal of the American Chemical Society that they had applied this strategy to the design of inhibitors of calpain that were based on calpastatin, an intrinsically unstable polypeptide that becomes structured upon binding to the enzyme. A two-turn alpha-helix that binds proximal to the active site cleft was stabilized, resulting in a potent and selective inhibitor for calpain. They expanded the utility of this inhibitor by developing irreversible calpain family activity-based probes, which retained the specificity of the stabilized helical inhibitor.

"We have an interest in this protein because it is important for Plasmodium development," said senior author Dr. Doron Greenbaum, assistant professor of pharmacology at the University of Pennsylvania. "We initially found that calpain played a role in parasites being able to get out of their host cell, so we became interested in inhibitor development for human calpains."

"Traditionally people thought that alpha-helices normally make horrible inhibitors because it was thought that proteases do not like to bind to them, preferring to bind motifs called a beta-sheet," said Dr. Greenbaum. "We decided to take a different tack on inhibitor development, which has traditionally been designing small peptide-like inhibitors that fit across an enzyme’s active site. We found that there was a small alpha-helix that fit into the active site of the calpain enzyme. It is the first example of an alpha-helical inhibitor of any protease. Previously no one has ever tried using an alpha-helical motif. It opens up a new way of inhibiting proteases."

Related Links:

Queen's University
University of Pennsylvania
University of California, San Francisco


Gold Member
Chagas Disease Test
CHAGAS Cassette
Verification Panels for Assay Development & QC
Seroconversion Panels
New
TETANUS Test
TETANUS VIRCLIA IgG MONOTEST
New
Coagulation Analyzer
CS-2400

Print article

Channels

Clinical Chemistry

view channel
Image: The tiny clay-based materials can be customized for a range of medical applications (Photo courtesy of Angira Roy and Sam O’Keefe)

‘Brilliantly Luminous’ Nanoscale Chemical Tool to Improve Disease Detection

Thousands of commercially available glowing molecules known as fluorophores are commonly used in medical imaging, disease detection, biomarker tagging, and chemical analysis. They are also integral in... Read more

Immunology

view channel
Image: The cancer stem cell test can accurately choose more effective treatments (Photo courtesy of University of Cincinnati)

Stem Cell Test Predicts Treatment Outcome for Patients with Platinum-Resistant Ovarian Cancer

Epithelial ovarian cancer frequently responds to chemotherapy initially, but eventually, the tumor develops resistance to the therapy, leading to regrowth. This resistance is partially due to the activation... Read more

Microbiology

view channel
Image: The lab-in-tube assay could improve TB diagnoses in rural or resource-limited areas (Photo courtesy of Kenny Lass/Tulane University)

Handheld Device Delivers Low-Cost TB Results in Less Than One Hour

Tuberculosis (TB) remains the deadliest infectious disease globally, affecting an estimated 10 million people annually. In 2021, about 4.2 million TB cases went undiagnosed or unreported, mainly due to... Read more

Pathology

view channel
Image: The ready-to-use DUB enzyme assay kits accelerate routine DUB activity assays without compromising data quality (Photo courtesy of Adobe Stock)

Sensitive and Specific DUB Enzyme Assay Kits Require Minimal Setup Without Substrate Preparation

Ubiquitination and deubiquitination are two important physiological processes in the ubiquitin-proteasome system, responsible for protein degradation in cells. Deubiquitinating (DUB) enzymes contain around... Read more

Technology

view channel
Image: The HIV-1 self-testing chip will be capable of selectively detecting HIV in whole blood samples (Photo courtesy of Shutterstock)

Disposable Microchip Technology Could Selectively Detect HIV in Whole Blood Samples

As of the end of 2023, approximately 40 million people globally were living with HIV, and around 630,000 individuals died from AIDS-related illnesses that same year. Despite a substantial decline in deaths... Read more

Industry

view channel
Image: The collaboration aims to leverage Oxford Nanopore\'s sequencing platform and Cepheid\'s GeneXpert system to advance the field of sequencing for infectious diseases (Photo courtesy of Cepheid)

Cepheid and Oxford Nanopore Technologies Partner on Advancing Automated Sequencing-Based Solutions

Cepheid (Sunnyvale, CA, USA), a leading molecular diagnostics company, and Oxford Nanopore Technologies (Oxford, UK), the company behind a new generation of sequencing-based molecular analysis technologies,... Read more
Copyright © 2000-2025 Globetech Media. All rights reserved.