Archive for January, 2009

The structures for NaK channel protein

Monday, January 26th, 2009

It is worth to paste the abstract of a paper by Amer Alam and Youxing Jiang(web)

We report the crystal structure of the nonselective cation channel NaK from Bacillus cereus at a resolution of 1.6 Å. The structure reveals the intracellular gate in an open state, as opposed to the closed form reported previously, making NaK the only channel for which the three-dimensional structures of both conformations are known. Channel opening follows a conserved mechanism of inner helix bending using a flexible glycine residue, the gating hinge, seen in MthK and most other tetrameric cation channels. Additionally, distinct inter and intrasubunit rearrangements involved in channel gating are seen and characterized for the first time along with inner helix twisting motions. Furthermore, we identify a residue deeper within the cavity of the channel pore, Phe92, which is likely to form a constriction point within the open pore, restricting ion flux through the channel. Mutating this residue to alanine causes a subsequent increase in ion-conduction rates as measured by 86Rb flux assays. The structures of both the open and closed conformations of the NaK channel correlate well with those of equivalent K+ channel conformations, namely MthK and KcsA, respectively.

NaK is the only channel with both open and close conformations known. I thought there are some other such membrane proteins before.

It is 2009 already

Friday, January 2nd, 2009

What a fast aging time! And worst of all, I forgot to make any resolution before the new year. :-(
Anyway, happy and work hard everyday!