The Role of Arg13 in Protein Phosphatase M tPphA from Thermosynechococcus elongatus

Table 3

The specific activity of tPphA and Arg-13 variants towards three phosphopeptides. Reactions were performed in the buffer as described in Experimental Procedures (Subsection 2.3). Triplicate assays were used. ± indicates the standard error. The results were obtained from single preparations of the wild-type (WT) and variant tPphA purifications.

Classification of Arg-13 variants	Variants	Thr peptide nmol/min/μg	Ser peptide nmol/min/μg
Arg-13 changed to residues with electrically charged side chains	WT(R13R)	9.32±0.14	5.49±0.06
	R13K	5.09±0.10	1.67±0.01
	R13H	1.13±0.08	0.68±0.04
	R13D	1.12±0.03	0.59±0.01
Arg-13 changed to residues with polar uncharged side chains	R13S	1.47±0.02	1.07±0.02
	R13T	1.28±0.02	1.13±0.02
	R13N	1.13±0.06	0.78±0.03
	R13Q	0.91±0.05	0.65±0.03
Arg-13 changed to residues with hydrophobic side chains	R13A	1.40±0.02	0.81±0.01
	R13L	0.26±0.02	0.05±0.01
	R13I	1.67±0.01	0.90±0.01
	R13M	1.55±0.07	0.84±0.01
Arg-13 changed to residues with aromatic side chains	R13F	1.07±0.04	0.47±0.01
	R13W	0.84±0.03	0.65±0.01
	R13Y	0.91±0.01	0.89±0.02
Arg-13 changed to residues with special side chains	R13G	0.74±0.04	1.04±0.02
	R13C	1.21±0.03	0.98±0.03
	R13P	1.29±0.03	0.85±0.02