Structural and mechanistic investigations on Salmonella typhimurium acetate kinase (AckA): identification of a putative ligand binding pocket at the dimeric interface

Table 2 Structure refinement and validation statistics

Parameter	Form-I (unliganded)	Form-II (citrate-bound)
Resolution range (Å) ^a	50.0-2.70 (2.80-2.70)	50.0-1.90 (1.97-1.90)
No. of atoms
Protein / Water / EDO / CIT ^b	11748 / 204 / 16 / -	5838 / 442 / 16 / 13
R-factors (%) ^c
R_work / R_free	22.1 / 28.3	18.9 / 22.4
Correlation coefficient (%) ^d	85.4	94.1
Wilson B-factor (Å²)	53.4	41.9
Average B-factor (Å²)
Protein / Water / EDO / CIT	44.7 / 10.4 / 45.8 / -	36.1 / 44.2 / 56.4 / 33.9
RMS deviation
Bond length (Å)	0.006	0.014
Bond angle (°)	0.977	1.414
Dihedral angle (°)	5.024	5.908
Chiral-center restraints (Å³)	0.066	0.098
General planes (Å)	0.003	0.006
Coordinate error: Luzzati (Å)	0.412	0.237
Residues in Ramachandran map (% / number)
Most favoured region	89.1 / 1,228	90.9 / 610
Allowed region	10.9 / 150	8.8 / 59
Generously allowed region	0 / 0	0.3 / 2
Disallowed region	0 / 0	0 / 0

Refinement and validation statistics are from REFMAC5 [19] and PROCHECK [37].
^a Values for the highest resolution shell are given in parentheses.
^b EDO and CIT refer to ethylene glycol and citrate, respectively.
^c R_work = $Σ (|F_{obs}| - | F_{calc} |) / Σ |F_{obs}|$ ; R_free was calculated similarly by using 5% of the reflections that were excluded from the refinement.
^d Correlation coefficient = $\sum (F_{o} F_{c} - < F_{o} > < F_{c} >) / {(\sum ({F^{2}}_{o} - < F_{o} >^{2}) (\sum {F^{2}}_{c} - < F_{c} >^{2})]}^{1 / 2}$ .

ISSN: 1472-6807