DOD
Search
Discussions
Biomedical Jobmarket
News
DOD Alert
Edit DOD
 
ACCOUNT
Login
Register
Forgotten Password?
 
 
Differences in apparent pore sizes of low and high voltage-activated Ca2+ channels.
 
Diabetes OD > Diabetic Complications > Cardiovascular > Calcium > Calcium channel > Journal Article > Journal Article

(Journal Article): Differences in apparent pore sizes of low and high voltage-activated Ca2+ channels.
 
Cataldi M, Perez-Reyes E, Tsien RW (Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305-5345, USA)
 
IN: J Biol Chem 2002; 277(48):45969-45976
Impact Factor(s) of J Biol Chem: 6.355 (2004), 6.482 (2003), 7.258 (2001)

Fulltext:    HTML  PDF

ABSTRACT: Pore size is of considerable interest in voltage-gated Ca(2+) channels because they exemplify a fundamental ability of certain ion channels: to display large pore diameter, but also great selectivity for their ion of choice. We determined the pore size of several voltage-dependent Ca(2+) channels of known molecular composition with large organic cations as probes. T-type channels supported by the Ca(V)3.1, Ca(V)3.2, and Ca(V)3.3 subunits; L-type channels encoded by the Ca(V)1.2, beta(1), and alpha(2)delta(1) subunits; and R-type channels encoded by the Ca(V)2.3 and beta(3) subunits were each studied using a Xenopus oocyte expression system. The weak permeabilities to organic cations were resolved by looking at inward tails generated upon repolarization after a large depolarizing pulse. Large inward NH(4)(+) currents and sizable methylammonium and dimethylammonium currents were observed in all of the channels tested, whereas trimethylammonium permeated only through L- and R-type channels, and tetramethylammonium currents were observed only in L-type channels. Thus, our experiments revealed an unexpected heterogeneity in pore size among different Ca(2+) channels, with L-type channels having the largest pore (effective diameter = 6.2 A), T-type channels having the tiniest pore (effective diameter = 5.1 A), and R-type channels having a pore size intermediate between these extremes. These findings ran counter to first-order expectations for these channels based simply on their degree of selectivity among inorganic cations or on the bulkiness of their acidic side chains at the locus of selectivity.

TYPE OF PUBLICATION: Original article

Articles citing this article:



 
Respond on this Journal Article!
Hint: Your Response should directly apply to Differences in apparent pore sizes of low and high voltage-activated Ca2+ channels.. Please check, if this context applies best to your contribution. Otherwise click HERE to change to the appropriate subject area. The actual subject area is Journal Article.