Dynamic properties of actin. Structural changes induced by beryllium fluoride

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Beryllium fluoride (BeFx) serves as a phosphate analogue in nucleotide-binding proteins.
• Previous studies show BeFx binds F-actin and stabilizes actin filaments by affecting subdomain 2.
• The structural and functional consequences of BeFx binding to G-actin and F-actin require further investigation.

Purpose of the Study:

• To investigate BeFx-induced structural and functional changes in G-actin and F-actin.
• To elucidate the role of BeFx as a phosphate analogue in actin systems.
• To assess the impact of BeFx on actin's interaction with myosin.

Main Methods:

• Proteolysis studies (subtilisin, trypsin) on G-actin and F-actin.
• Chemical modification assays (Cys-374 alkylation).
• Enzyme activity assays (actin-activated ATPase) and in vitro motility assays.

Main Results:

• BeFx binding to MgADP-G-actin mimics MgATP-G-actin by altering subdomain 2 proteolysis patterns.
• BeFx strongly inhibits proteolysis in subdomain 2 of MgADP-F-actin, indicating cooperative structural stabilization.
• BeFx induces changes in subdomain 1 of F-actin and has minimal impact on actin-myosin interactions and motility.

Conclusions:

• BeFx acts as a phosphate analogue, inducing distinct structural changes in monomeric (G) and filamentous (F) actin.
• These BeFx-induced structural modifications highlight the dynamic nature of actin and differences between its monomeric and polymeric forms.
• Despite significant structural alterations, BeFx does not substantially affect actin's functional interaction with myosin.