SPACI score report for 1a21 in ASTRAL 2.07:

PDB Entry: 1a21
SPACI score: 0.35
AEROSPACI score: 0.35

Experiment type: XRAY
Resolution: 2.35
R-factor: 0.191
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 2
PCK3 PROCHECK H-bonds: 2
WCK1 WHAT_CHECK Packing: -1.425
WCK2 WHAT_CHECK Ramachandran: -2.767
WCK3 WHAT_CHECK Chi angles: -2.593
WCK4 WHAT_CHECK Backbone: -0.458

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).