Lattice mobility and anomalous temperature factor behaviour in cytochrome c'.

Area of Science:

• Structural Biology
• Biophysics
• X-ray Crystallography

Background:

• Atomic temperature factors (B-values) from X-ray refinement estimate protein mobility.
• B-values correlate with theoretical dynamics and experimental antibody reactivity.
• Comparing B-values to solution properties requires correcting for crystal environment effects.

Purpose of the Study:

• To investigate lattice effects on refined B-values.
• To compare crystallographically independent subunits of dimeric cytochrome c' from Rhodospirillum molischianum.

Main Methods:

• X-ray refinement of dimeric cytochrome c'.
• Analysis of B-values in crystallographically independent subunits.
• Assessment of local and lattice-induced mobility differences.

Main Results:

• Lattice disordering effects influence refined B-values.
• B-value differences up to 12 A were observed between subunits.
• Concerted rotations of molecules about a crystal symmetry axis contribute to B-value variations.

Conclusions:

• Crystal lattice effects, including disorder and molecular rotations, significantly alter apparent protein mobility as measured by B-values.
• Careful consideration of crystal packing is crucial when interpreting B-values for protein dynamics.