Extension of Rapid Buffering Approximation to Ca2+ Buffers with Two Binding Sites

摘要: Abstract Fundamental cell processes such as synaptic neurotransmitter release, endocrine hormone secretion, and myocyte contraction are controlled by highly localized calcium (Ca 2+ ) signals resulting from brief openings of trans-membrane Ca channels. On short temporal spatial scales, the corresponding local nanodomains formed in vicinity a single or several open channels can be effectively approximated quasi-stationary solutions. The rapid buffering approximation (RBA) is one most powerful approximations, based on assumption instantaneous equilibration bimolecular reaction, combined with conservation condition for total buffer molecule numbers. Previously, RBA has been generalized to an arbitrary arrangement flat membrane, presence any number simple buffers one-to-one binding stoichiometry. However, many biological have multiple sites. For example, sensors phylogenetically related calmodulin consist two -binding domains (lobes), each domain ions cooperative manner. Here we consider extension interdependent We show that buffers, solution given cubic equation, analogous quadratic equation describing case simple, buffer. examine detail dependence accuracy parameters, reveal conditions under which provides sufficient precision.