Related Experiment Videos
Protein diffusivities in skinned frog skeletal muscle fibers
1Department of Physiology & Biophysics, University of Vermont School of Medicine, Burlington 05405.
Advances in Experimental Medicine and Biology
|January 1, 1988
Summary
Muscle cytoplasm significantly slows protein diffusion compared to solutions. This reduced protein mobility is likely due to factors like tortuosity, viscosity, and binding within the muscle cell environment.
Area of Science:
- Muscle physiology
- Biochemistry
- Cell biology
Background:
- Proteins diffuse slower in muscle cytoplasm than in aqueous solutions.
- Understanding this phenomenon is crucial for muscle function.
- Previous studies lacked detailed analysis of intracellular diffusion barriers.
Purpose of the Study:
- Investigate the reasons behind reduced protein diffusion in muscle cytoplasm.
- Quantify the diffusion rates of specific proteins within muscle fibers.
- Elucidate the factors contributing to hindered protein mobility.
Main Methods:
- Utilized microvolumetric sampling to fractionate muscle cytoplasm into cytosol and cytomatrix.
- Employed electrophoretic mobility to identify diffusible proteins.
- Measured apparent diffusion coefficients of proteins in skinned muscle fibers and aqueous solutions.
Main Results:
- Identified glyceraldehyde-3-phosphate dehydrogenase, triose-P-isomerase, phosphoglycerate mutase, and parvalbumin as diffusible proteins.
- Apparent diffusion coefficients in skinned fibers were ~10% or less of those in aqueous solutions.
- The diffusion of parvalbumin (a Ca2+ chelator) mirrored Ca2+ diffusion, suggesting a complex.
Conclusions:
- Reduced protein diffusivity in muscle cytoplasm is attributed to tortuosity and viscosity.
- Binding to cytomatrix proteins or sarcoplasmic reticulum may also impede diffusion.
- The slow diffusion of Ca2+ in muscle is likely due to its complex with parvalbumin.