TABLE 2.

Comparison of calculated and experimental masses of the subtilisin cleavage products of wild-type and Y/E actin

The 60-min digestion mixtures of WT and Y/E (Fig. 2) were analyzed by mass spectrometry. The N- and C-terminal peptides expected from cleavage between Met-47 and Gly-48 were found in both samples. The Y/E sample had an additional, minor C-terminal peptide consistent with cleavage between Leu-67 and Lys-68; a corresponding N-terminal peptide was not detected.

Actin	Residues	Calculated mass	Experimental mass
		Da	Da
WT	Acetyl-1–47a	4,844.5	4,844.1
	48–375	36,831.2	36,830.2
Y/E	Glycyl-1–47b	4,859.5	4,859.2
	48–375	36,797.1	36,796.7
	68–375	34,683.8	34,682.8

^a Mass includes an N-terminal acetyl group.

^b Mass includes an N-terminal glycyl group.