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Published on: March 16, 2017
Surface charge, fluidity, and calcium uptake by rat intestinal brush-border vesicles
H P Schedl1, K K Christensen, E D Clark
1VA Medical Center, Iowa City, IA.
Biochimica Et Biophysica Acta
|March 8, 1995
Summary
Positively charged polyarginine affects calcium uptake by altering membrane fluidity. It inhibits saturable calcium uptake while increasing non-saturable uptake, suggesting a role for surface charge in ion transport.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Biological membranes possess negative surface charges that interact with calcium ions during uptake.
- Polycations like polyarginine bind membranes with high affinity, potentially displacing calcium.
Purpose of the Study:
- To investigate the impact of polyarginine on calcium uptake in brush-border membrane vesicles.
- To correlate these effects with changes in membrane fluidity.
Main Methods:
- Utilized brush-border membrane vesicles for calcium uptake studies.
- Employed electron paramagnetic resonance (EPR) to assess membrane fluidity.
- Analyzed calcium uptake kinetics under varying polyarginine concentrations.
Main Results:
- Polyarginine inhibited the saturable component of calcium uptake via a mixed competitive/non-competitive mechanism.
- Polyarginine increased the rate constant (kD) for non-saturable calcium uptake in a concentration-dependent manner.
- These alterations in calcium uptake correlated with decreased membrane fluidity.
Conclusions:
- Surface negative charge plays a critical role in both saturable and non-saturable calcium uptake.
- Changes in membrane fluidity influence calcium uptake dynamics.
- Polyarginine's concentration-dependent stimulation of non-saturable uptake suggests a potential gating mechanism.
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