Аннотация
RyR and InsP3R are Ca$^2+$-release channels. When induced to open
by the appropriate stimulus, these channels allow Ca$^2+$ to
leave intracellular storage organelles at an astonishing rate. Investigations
of the ion-handling properties of isolated RyR channels have demonstrated
that, at least in comparison to voltage-gated channels of surface
membranes, these channels display limited powers of discrimination
between physiologically relevant cations and this relative lack of
selectivity is likely to contribute to the ability of Ca$^2+$-release
channels to maintain high rates of cation translocation without compromising
function. A range of ion-handling properties in RyR are consistent
with the proposal that this channel functions as a single-ion channel
and theoretical considerations indicate that the high rates of ion
translocation monitored for RyR would require the pore of such a
structure to be short and possess a large capture radius. Measurements
of the dimensions of regions of RyR involved in ion conduction and
discrimination indicate that this is likely to be the case. In each
monomer of RyR/InsP3R, residues making up the last two trans-membrane
spanning domains and a luminal loop linking these two helices contribute
to the formation of the channel pore. The luminal loops of both RyR
and InsP3R contain amino acid sequences similar to those known to
form the selectivity filter of K$^+$ channels. In addition the
luminal loops of both Ca$^2+$-release channels contain sequences
that are likely to form helices that may be analogous to the pore
helix visualised in KcsA. The correlation in structural elements
of the luminal loops of RyR/InsP3R and KcsA has prompted us to speculate
on the tertiary arrangement for this region of the Ca$^2+$-release
channels using the established structure of KcsA as a framework.
- 11388090
- and
- animals,
- binding
- calcium
- calcium,
- calmodulin,
- channel
- channel,
- channels,
- conformation,
- cytoplasmic
- gating,
- gov't,
- humans,
- ion
- l-type,
- models,
- molecular,
- non-u.s.
- nuclear,
- protein
- proteins,
- receptor
- receptors,
- release
- research
- ryanodine
- sites,
- support,
- tacrolimus
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