In
this work, we illus
tra
te
the abili
ty of
the prokaryo
tic po
tassium channel KcsA
to assemble in
to a varie
ty of supramolecular clus
ters of defined sizes con
taining
the
te
trameric KcsA as
the repea
ting uni
t. Such clus
ters, par
ticularly
the larger ones, are markedly de
tergen
t-labile and
thus, disassemble readily upon exposure
to
the de
tergen
ts commonly used in pro
tein purifica
tion or conven
tional elec
trophoresis analysis. This is a reversible process, as clus
ter re-assembly occurs upon de
tergen
t removal and wi
thou
t the need of added membrane lipids. In
teres
tingly,
the dimeric ensemble be
tween
two
te
trameric KcsA molecules are qui
te resis
tan
t to de
tergen
t disassembly
to individual KcsA
te
tramers and along wi
th
the la
tter, are likely
the basic building blocks
through which
the larger clus
ters are organized.
As to the proteins domains involved in clustering, we have observed disassembly of KcsA clusters by SDS-like alkyl sulfates. As these amphiphiles bind to inter-subunit, ¡°non-annular¡± sites on the protein, these observations suggest that such sites also mediate channel-channel interactions leading to cluster assembly.