 |
|
Title
|
|
Capping and alpha-helix stability.
|
|
|
Authors
|
|
L.Serrano,
A.R.Fersht.
|
|
|
Ref.
|
|
Nature, 1989,
342,
296-299.
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The first and last four residues of alpha-helices differ from the rest by not
being able to make the intrehelical hydrogen bonds between the backbone greater
than C=O groups of one turn and the greater than NH groups of the next.
Physico-chemical arguments and statistical analysis suggest that there is a
preference for certain residues at the C and N termini (The C- and N-caps) that
can fulfil the hydrogen bonding requirements. We have tested this hypothesis by
constructing a series of mutations in the two N-caps of barnase (Bacillus
amyloliquefaciens ribonuclease, positions Thr 6 and Thr 26) and determining the
change in their stability. The N-cap is found to stabilize the protein by up to
approximately 2.5 kcal mol(-1). The presence of a negative charge of the N-cap
adds some 1.6 kcal mol(-1) of stabilization energy because of the interaction
with the macroscopic electrostatic dipole of the helix.
|
|
|
|