Question: How many proteins in cytoplasm/membrane?

Cornelius Krasel phak004 at wrzx15.rz.uni-wuerzburg.de
Wed Jul 5 13:31:14 EST 1995


henrik at silibone.cchem.berkeley.edu wrote:
> In a typical eukaryotic cell, how many proteins are there in the cytoplasm?
> (numbers or conc.)
> How many proteins are there in the cell membrane?
> What would be a typical conc. of a regulatory/enzymatic/structural protein
> in the eukaryotic cell?
> If a protein is overexpressed in a eukaryotic cell, how high
> concentrations can be achieved (without killing the cell)?
> Has anyone tried to overexpress a membrane protein, and how many copies
> would the cell accept in its membrane?

> By the way: What are the approximate sizes of various types of
> eukaryotic cells?

Some of these questions are covered in cell biology books like Alberts et
al. or Darnell et al. I think there was also a review in TIBS a few years ago
which explicitely dealt with the concentration of proteins in the
cytoplasm (the title page of that issue showed an enormously crowded
bacterial cell with its interior crowded with ribosomes and soluble
proteins).

I would assume that in an Sf9 cell you can get expression rates of
soluble proteins up to 10--20% of total soluble protein. However,
Sf9 cells are killed during the expression, so this might not be
the answer you want.

Related to the topic of membrane protein overexpression:
Generally, cells are rather reluctant to overexpress membrane proteins,
for unknown reasons. There are a few exceptions, however. Gebhard
Schertler has published an excellent review on membrane protein overexpression
a few years ago:

@article{schertler:92a,
        author  = {Gebhard F. X. Schertler},
        title   = {Overproduction of membrane proteins.},
        journal = {Curr. Op. Struct. Biol.},
        volume  = 2,
        pages   = {534--544},
        year    = 1992,
}

Hope that helps,
--Cornelius.

--
/* Cornelius Krasel, Institut f. Pharmakologie, Versbacher Str. 9, D-97078 */
/* Wuerzburg, Germany                email: phak004 at rzbox.uni-wuerzburg.de */
/* "Science is the game you play with God to find out what His rules are." */



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