querjek - 25-7-2011 at 22:11
Hey all,
Does anybody out there know of any proteins with the same (or similar) primary structure but different functions? I was thinking about proteins before
going to bed last night and this question came up.
Thanks!
chemoleo - 26-7-2011 at 12:23
Well a protein with identical sequence (primary structure...) will have identical functions - but it may be context dependent, i.e. it could exert a
different function in the nucleus than it does in the cytoplasm of a cell...
fledarmus - 26-7-2011 at 13:33
I can think of three possible cases off the top of my head which might be partial answers to your question:
1)There are pleiotropic proteins which have multiple functions depending on when and where they are expressed and what other signalling proteins are
present.
2) There are also which dimerize or trimerize before they have any activity, and they may have different functions depending on whether they are
homodimers or heterodimers. Homodimers are dimers formed from two identical proteins, heterodimers are dimers formed from two different proteins.
3) And then there are proteins which may have several different modes of post translational modification. Once the protein is expressed, it must
usually be modified by other proteins before it can function. For example, some proteins can function either as soluble signalling proteins or as
membrane-bound signalling proteins, depending on whether a specific chemical modification is made that localizes the protein to the cell membrane. The
two signalling processes may have completely different functions.
There are also some diseases caused by mis-folding of proteins, typically due to absence of the appropriate chaperone proteins, and two proteins with
identical primary structure might act very differently in the cells due to different tertiary structure.