Journal
BIOPHYSICAL JOURNAL
Volume 103, Issue 7, Pages 1616-1625Publisher
CELL PRESS
DOI: 10.1016/j.bpj.2012.08.050
Keywords
-
Categories
Funding
- National Institutes of Health [R01-HL095122, P50-GM094503, T32-HL094273]
Ask authors/readers for more resources
Mitochondrial adenine nucleotide (AdN) content is regulated through the Ca2+-activated, electroneutral ATP-Mg/P-i carrier (APC). The APC is a protein in the mitochondrial carrier super family that localizes to the inner mitochondrial membrane (IMM). It is known to modulate a number of processes that depend on mitochondrial AdN content, such as gluconeogenesis, protein synthesis, and citrulline synthesis. Despite this critical role, a kinetic model of the underlying mechanism has not been developed and validated. Here, a biophysical model of the APC is developed that is thermodynamically balanced and accurately reproduces a number of reported data sets from isolated rat liver and rat kidney mitochondria. The model is based on an ordered bi-bi mechanism for heteroexchange of ATP and P-i and includes homoexchanges of ATP and P-i to explain both the initial rate and time course data on ATP and P-i transport via the APC. The model invokes seven kinetic parameters regarding the APC mechanism and three parameters related to matrix pH regulation by external P-i. These parameters are estimated based on 19 independent data curves; the estimated parameters are validated using six additional data curves. The model takes into account the effects of pH, Mg2+, and Ca2+ on ATP and P-i transport via the APC, and supports the conclusion that the pH gradient across the IMM serves as the primary driving force for AdN uptake or efflux. Moreover, computer simulations demonstrate that extramatrix Ca2+ modulates the turnover rate of the APC and not the binding affinity of ATP, as previously suggested.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available