as indicated by
greater loss in peak volume for rigid residues than partially mobile
residues. The greatest mobility was observed in the CypA binding
loop, consistent with our own results. 15N–15N backbone dipolar
recoupling (15N-BARE) experiments were utilized for the measurement
of the torsion angles wi and wi1 (and ui to an extent). While
most a-helical residues exhibited rapid dephasing due to relatively
short interhelical distances, some residues displayed slower dephasing times, indicative of extended backbone conformations,
illustrated in Fig. 9. Using TALOS + torsion angle predictions [108]
and the 15N-BARE data as restraints [109], structure calculations
of CA were run with Xplor-NIH [110] and revealed that the 310-
helix near the CTD–NTD linker is in a more extended conformation
than indicated in solution NMR studies, and also distinguished differences
in the loops between H3 and H4 and H10 and H11