Thermodynamic effects of phospholamban on Ca-ATPase kinetics

The Ca-ATPase of sarcoplasmic reticulum removes cytosolic calcium to promote muscle relaxation. In the heart, the Ca-ATPase is regulated by phospholamban, which inhibits the Ca-ATPase by decreasing Ca-ATPase calcium sensitivity. However, the kinetic and thermodynamic mechanisms of inhibition are not understood. The purpose of this research was to test the hypothesis that phospholamban regulates Ca-ATPase kinetics by increasing Ca-ATPase activation energy. The baculovirus-insect cell expression system was used to produce samples containing Ca-ATPase alone or Ca-ATPase with phospholamban. The temperature-dependence of Ca-ATPase activity and catalytic site density was measured in the absence and presence of phospholamban at sub-saturating calcium and used to calculate the temperature-dependence of Ca-ATPase turnover. Arrhenius analyses showed that phospholamban increased Ca-ATPase activation energy from 31 +/- 3 J/mol (Ca-ATPase only) to 52 +/- 5 J/mol (Ca-ATPase + phospholamban). The results supported the hypothesis and provided new insight into the mechanism of phospholamban inhibition of Ca-ATPase.

Name thesis:degree_name

MS

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biochemistry

Year dc:date.available

2002

Author dc:creator

• Apopa, Patrick L.

Contributors dc:contributor

• Jim Mahaney.

• Biochemistry

Identifier

https://researchrepository.wvu.edu/etd/1570

OAI identifier oai:identifier

oai:researchrepository.wvu.edu:etd-2573