Msp. Sansom et Id. Kerr, TRANSBILAYER PORES FORMED BY BETA-BARRELS - MOLECULAR MODELING OF PORE STRUCTURES AND PROPERTIES, Biophysical journal, 69(4), 1995, pp. 1334-1343
Transmembrane beta-barrels, first observed in bacterial porins, are po
ssible models for a number of membrane channels. Restrained molecular
dynamics simulations based on idealized C alpha beta templates have be
en used to generate models of such P-barrels. Model beta-barrels have
been analyzed in terms of their conformational, energetic, and pore pr
operties. Model beta-barrels formed by N = 4, 8, 12 and 16 anti-parall
el Ala(10) strands have been developed. For each N, beta-barrels with
shear numbers S = N to 2N have been modeled. In all beta-barrel models
the constituent beta-strands adopt a pronounced right-handed twist. I
nterstrand interactions are of approximately equal stability for all m
odels with N greater than or equal to 8, whereas such interactions are
weaker for the N = 4 beta-barrels. In N = 4 beta-barrels the pore is
too narrow (minimum radius similar to 0.6 Angstrom) to allow ion perme
ation. For N greater than or equal to 8, the pore radius depends on bo
th N and S; for a given value of N an increase in S from N to 2N is pr
edicted to result in an approximately threefold increase in pore condu
ctance. Calculated maximal conductances for the beta-barrel models are
compared with experimental values for porins and for K+ channels.