by Happydadtoo » Sun Nov 11, 2007 4:49 pm
Hi!
H-bonds provide the secondary structure of the protein - they create the alpha helix which makes up most of most proteins and the beta-pleated sheet which makes up a FEW (always extracellular and structural) proteins.
They also make up most of the tertiary structure too (though disulphide bridges also help here. Because H-bonds needs H atoms (doh!) and some of these change position with pH, the tertiary structure of a protein changes shape with pH and so therefore, does the shape of the active site. So..... H-bonds explain the pH curve of a typical enzyme.
The hydrophobic amino-acids collect towards the centre of the ptrotein, excluding water AND/OR are the exposed amino-acids in proteins which are embedded in membranes (and thus surrounded by lipid).
The hydrophyllic amino-acids are on the outside, where they are exposed to water AND form the central 'tube' of channel proteins in membranes.
They have some other uses too - histones wrap themselves around DNA and that interaction is helped by hydrophobic amino-acids as well as the basic ones (which react with the acidic phosphate groups on the DNA).
Hope that all helps a little
HD2