At Rice University and Baylor College of Medicine (BCM), structural biologists have captured the first three-dimensional crystalline snapshot of a critical but fleeting process that takes place thousands of times per second in each human cell.
The research appears online today in the journal Cell Reports
and could prove useful in the study of cancer and other diseases.
The biological "freeze-frame" shows the initial step in the formation of actin, a sturdy strand-like filament that is vital for humans. Actin filaments help cells maintain their shape. The filaments, which are called F-actin, also play key roles in muscle contraction, cell division and other critical processes.
"One of the major distinctions between cancerous cells and healthy cells is their shape," said study co-author Jianpeng Ma, professor of bioengineering at Rice and the Lodwick T. Bolin Professor of Biochemistry at BCM. "There is a correlation between healthy shape and well-regulated cell growth, and cancer cells are often ugly and ill-shaped compared to healthy cells."
F-actin was discovered in 1887, but despite the more than 18,000 actin-related studies in scientific literature, biologists have struggled to unlock some of its secrets. For example, F-actin is a polymer made of many smaller proteins called monomers. These building blocks, which are called G-actin, self-assemble end to end to form F-actin. But the self-assembly process is so efficient that scientists have been unable to see what happens when the first two or three monomers come together to form the nucleus of a filament. The F-actin filaments inside cells are constantly being built, torn apart and rebuilt.