(Solved) How can a protein with no signal peptide be integrated into the plasma membrane as a transmembrane protien?

smokinjoe531

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11 years ago

How can a protein with no signal peptide be integrated into the plasma membrane as a transmembrane protien?

I am studying a protein in Neurospora crassa known as prm1. This protein has been identified in yeast as a transmembrane glycoprotein involved in cell fusion (it is a homolog to N. crassa prm1). Its method of action seems to be the stablaization of membrane pores that allow for cell fusion, and in its absence cell fusion of yeast can still occur. From computer predictions prm1 in N. crassa appears to have 5-6 transmembrane domains, however no signal peptide has been predicted from any program. How could this protein become integrated into the endomembrane system and later the plasma membrane if it lacks a signal peptide?

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bugbugs4

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11 years ago

As far as we know, that's pretty close to impossible. How sure are you that there's no signal, especially since its a computer simulation? there has to be some sort of post-translational modification as it comes out of hte endomembrane...

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nursing2

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11 years ago

This verified answer contains over 140 words.

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lenazoni20

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11 years ago

Good question. Our protein (Alix in mammals) has the same issue. It's known to be membrane associated, can actually directly bind phosphatidic acids (LBPA), but doesn't have a signal peptide. It's possible your protein also does this. Different fatty acids are at different concentrations in different membranes, so this may be one explaination why some proteins are selectively bound to specific membranes. The fact that it has 5-6 TM domains is a good clue that it's a membrane protein. It may also have chaperon proteins which escort it to the membrane. So, not all proteins need a signal peptide. Too bad, it makes our life more difficult. You could always subclone the protein and figure out what domain binds to the membrane, and if the binding occurs in vitro or not.

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