Table 1. Specific activity of mouse MsrB1-Cys and its mutant forms.

Protein form	Specific activity (nmol/min/mg protein)
MsrB1-Cys	1.5±0.1
MsrB1-Cys-Xa	3.3±0.1
Cleaved MsrB1-Cys-Xa	ND

Catalytic activity of purified recombinant proteins was determined using dabsyl-Met-RO as substrate. MsrB1-Cys: Cys mutant of mouse MsrB1, MsrB1-Cys-Xa: Cys mutant of MsrB1 engineered to contain a factor Xa cleavage site inserted in the coding region between Gly75 an Asn76. Cleaved MsrB1-Cys-Xa: MsrB1-Cys-Xa cleaved with factor Xa. ND: not detected.