发信人: doggiebear (doggiebear), 信区: Biology
标 题: Re: SBIG: Channels
发信站: Unknown Space - 未名空间 (Thu Oct 16 22:09:42 2003) WWW-POST

【 在 space (排骨教主) 的大作中提到: 】
: 明白一点了.
:
: 【 在 doggiebear (doggiebear) 的大作中提到: 】
: : Cell has a Na/K pump. Basically it used ATP (energy) to pump out Na and
pump
: : in K. Actually cell uses large amount of energy to establish such
gradient.
:
: pump需要通过某种通道进行吗? 基本上能算出ATPpump K+需要作的功来:
K*T*Log[100/4],
: 大概是3 K T.室温下ATP hydrolysis释放的能量是几个KT?
:
:

This is a very good question. i don't know how the pump look like, since no
structure about pump as I know has been solved. I have to say, it is very
likely it has some kind of channel like structure. remeber the potassium
channel? It has two configurations, one for high K and the other for low K. So
I can envision the pump should at least have two configurations.

Just suppose there is a potassium pump, it tries to do work against the
gradient, literally by pumping K into the cell.

So configuration one, this is a K high affinity configuration. It faces the
outside, binds K and triggers ATP hydrolysis.
ATP hydrolysi changes it to configuration II. Now it faces the cell. This is K
low affinity configuration. So it releases K. Then it converts back to
configuration 1.

The actually picture may be more complex.

but the discovery of mackinon on two configuration of K channel do give me an
insight. It is on the first paper (nature vol 414 page 43) figure 5.

--
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