SPACI score report for 2b91 in ASTRAL 2.05:

PDB Entry: 2b91
SPACI score: 0.43
AEROSPACI score: 0.43

Experiment type: XRAY
Resolution: 2
R-factor: 0.208
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 2
PCK3 PROCHECK H-bonds: 1
WCK1 WHAT_CHECK Packing: -0.549
WCK2 WHAT_CHECK Ramachandran: 0.047
WCK3 WHAT_CHECK Chi angles: -3.076
WCK4 WHAT_CHECK Backbone: 0.05

Note: Here are links to pages about PROCHECK and WHAT_CHECK.

Here is the full WHAT_CHECK report on this protein (linked from the WHAT_CHECK site).