SPACI score report for 4kb8 in ASTRAL 2.06:

PDB Entry: 4kb8
SPACI score: 0.44
AEROSPACI score: 0.44

Experiment type: XRAY
Resolution: 1.95
R-factor: 0.207
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 2
PCK3 PROCHECK H-bonds: 2
WCK1 WHAT_CHECK Packing: 0.215
WCK2 WHAT_CHECK Ramachandran: -0.169
WCK3 WHAT_CHECK Chi angles: -1.43
WCK4 WHAT_CHECK Backbone: 3.712

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).