figure to the left shows the structure of Ca2+-CaM complexed with
the CaM-binding domain peptide (P) from rabbit smooth muscle myosin light chain
kinase determined by NMR spectroscopy.
Notice how the central linker domain (LD) acts as a flexible tether to
allow CaM to interact with the target peptide. In this end-on
view of the structure, the channel formed by CaM through which
the MLCK peptide runs is lined with hydrophobic residues. Interaction of these residues with
hydrophobic amino acids in the target peptide accounts for ~80% of the contacts
between CaM and MLCK. This mechanism of interaction accounts
for the tremendous amino acid sequence variation in the CaM-binding domains of
target proteins. This is because hydrophobic interaction can accommodate a
wider number of amino acid residue interactions than charge-charge interaction
have trouble visualizing CaM-target peptide interaction from the molecular
model shown in the figure, click here
to see a "cartoon" version that might help.
structure was reproduced from atomic coordinates deposited in the Brookhaven Protein Data Bank
(structure code 2BBN) using the program Rasmol.
even better look at this structure, click here to view a model that you can rotate and manipulate based
on the NMR structure of apo-calmodulin.
this structure, you will need to have installed Chemscape Chime or Rasmol, which are
both free plug-ins for viewing molecular structures.
1998 Ray Zielinski