Can we calculate the exact number of receptors on E.Coli membrane?

[Eagle9]

I have heard that nobody really knows how many receptors are placed on E.Coli cell membrane. Of course we know the general types of the proteins incorporated in membrane (Carrier proteins, Na+/K+-ATPase, various transporters, Ion channels) but I need to know the exact number of types and exact total number of receptors on E.Coli membrane. Actually there is a article in Wikipedia but it does not give us this number.

So, what can you tell me about this? Has anybody counted them? If there is a better web-forum for microbiology then tell me and I will post this question there

 

[Ygggdrasil]

The following paper has measured the copy number of nearly every protein in E. coli:

Taniguchi et al. 2010 Quantifying E. coli Proteome and Transcriptome with Single-Molecule Sensitivity in Single Cells. Science 329: 533. doi:10.1126/science.1188308.

 

[Andy Resnick]

<snip> I need to know the exact number of types and exact total number of receptors on E.Coli membrane. <snip>

Why do you think this number would remain constant for any meaningful length of time? Proteins degrade and are replaced. Expression levels vary in response to environmental cues. Cells are not time-independent objects.

 

[Eagle9]

Please tell me why we cannot simply count the number of receptors? Cannot the Scanning probe microscope or the Scanning electron microscope scan the plasmatic membrane and see any roughness on it? Such roughness would be the receptors.

Ygggdrasil

The following paper has measured the copy number of nearly every protein in E. coli:

I quickly reviewed it twice but there are no exact and direct data of how many receptors are placed on the membrane. They say:

The fluorescence images show the intracellular localization of protein (Fig. 1, C to E).Most
cytoplasmic proteins were uniformly distributed intracellularly (Fig. 1C), whereas manymembranebound or periplasmic proteins showed localization
along the outer contours of the cell (Fig. 1D and table S3). Other proteins, including some
DNA-bound proteins and low-copy membrane proteins, showed punctate localization (Fig. 1E).

but this is not what I actually want.

Did I miss something there?

Andy Resnick

Why do you think this number would remain constant for any meaningful length of time? Proteins degrade and are replaced. Expression levels vary in response to environmental cues. Cells are not time-independent objects.

No, I do not think this, but still I want to know the number (at least variable number and not constant) of receptors on the membrane.

 

[Ygggdrasil]

Please tell me why we cannot simply count the number of receptors? Cannot the Scanning probe microscope or the Scanning electron microscope scan the plasmatic membrane and see any roughness on it? Such roughness would be the receptors.

E. coli are gram negative bacteria, meaning they have an inner membrane and an outer membrane. Scanning probe microscopes (if they have the ability to detect these proteins) would be able to count only the outer membrane proteins. Furthermore, they would not be able to distinguish between the different types of outer membrane proteins.

I quickly reviewed it twice but there are no exact and direct data of how many receptors are placed on the membrane. They say:

but this is not what I actually want.

Did I miss something there?

The information in table S6 should allow you to calculate the mean number of each protein in the E. coli strains they measured. All you need to do is compare that data to a list of E. coli membrane proteins.The bionumbers database, says the there are ~200000 proteins in the inner membrane of E. coli and ~300000 proteins in the outer membrane: http://bionumbers.hms.harvard.edu//bionumber.aspx?id=100083&ver=3

 

[Eagle9]

Ygggdrasil

E. coli are gram negative bacteria, meaning they have an inner membrane and an outer membrane. Scanning probe microscopes (if they have the ability to detect these proteins) would be able to count only the outer membrane proteins. Furthermore, they would not be able to distinguish between the different types of outer membrane proteins.

Ok, let such microscope do it, is it possible? It will simply move along the outer membrane and it will ”feel” something on the membrane, this “something” will be receptor. Has anybody tried to do it?

The information in table S6 should allow you to calculate the mean number of each protein in the E. coli strains they measured. All you need to do is compare that data to a list of E. coli membrane proteins.

Where is possible to find them?

The bionumbers database, says the there are ~200000 proteins in the inner membrane of E. coli and ~300000 proteins in the outer membrane: http://bionumbers.hms.harvard.edu//b...d=100083&ver=3

Thanks, this latter information is valuable; I think I can trust this web-site