SPACI score report for 4gu6 in ASTRAL 2.05:

PDB Entry: 4gu6
SPACI score: 0.49
AEROSPACI score: 0.49

Experiment type: XRAY
Resolution: 1.95
R-factor: 0.171
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 1
PCK3 PROCHECK H-bonds: 2
WCK1 WHAT_CHECK Packing: -0.468
WCK2 WHAT_CHECK Ramachandran: 0.172
WCK3 WHAT_CHECK Chi angles: -0.42
WCK4 WHAT_CHECK Backbone: 4.06

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).