Micro-environment in cell nucleus

[Monique]

Is it known what the salt conditions are like in the nucleus? For instance, in the cytoplasm [KCl]=100mM [NaCl]=10mM.. would this be very different in the nucleus?

Which salts would be important in influencing protein/protein or protein/DNA interactions?

[iansmith]

From what I've seen, [KCl]=50 mM but it varies, also [NaCl]=100mM because the DNA-histone-complex is only stable for a certain concentration between 20 and 500 mM, and the optimum is 100 mM.

As far as the best salt for influencing the protein-protein and -DNA interactions, it will depend on the protein or DNA, the pH and the microenvironment.

[Monique]

100 mM NaCl? That is a lot.. How large are the nuclear pores, are ions able to pass through? Ion pumps known to exist in it? You'd think there must be a lot of cations in the nucleus to compensate for the negative charge of the DNA.

As far as the best salt for influencing the protein-protein and -DNA interactions, it will depend on the protein or DNA, the pH and the microenvironment.
That's why I ask what conditions in the nucleus are like :)

[iansmith]

For instance, in the cytoplasm [KCl]=100mM [NaCl]=10mM..

I think you are underestimating [NaCl], it should be closer to 100 mM rather than 10 mM. There is also a lot of gradient within the cytoplasm and 100 mM would be an average. The concentration probably goes from 10 mM to 800 mM in the cytoplasm depending of the location. it is propably the same with the nucleus.

[Monique]

I am pretty sure the cell keeps the concentration of Na+ low and K+ high, to balance osmosis and provide countercharge.

Why do you think the concentration can depend so much on the location in the cytoplasm?

Have you ever heard of ion-pumps in the nuclear envelope membrane? Since it disintegrates and re-assembles during mitosis there should be some if the conditions in the nucleus are specialized. Or maybe I should go discover them myself and receive a nobel prize for it :wink: maybe it's just sitting in a textbook waiting to be read..

[iansmith]

I am pretty sure the cell keeps the concentration of Na+ low and K+ high, to balance osmosis and provide countercharge.

If I am correct, it is relative to the external enviroment. The extracellular enviroment has [NaCl]=150 mM.

Why do you think the concentration can depend so much on the location in the cytoplasm?

Not all biochemicals reactions requires the same amount of salt concentration and some reaction are more sensitive to certain concentration. The intracellular space is quite fluid and ions move a lot and not necessarly in gradient dependent manner. The compartmentalization is also seen in bacteria.

Have you ever heard of ion-pumps in the nuclear envelope membrane?

Not as far as I remember but I will to reread my cell bio text book