TABLE 2.

Mass spectrometric identification of proteasome-mediated degradation products from GGQ₇RR and Fl-GGQ₇RR

Human red cell 20 S proteasomes (4 μg) and 18 μg of PA28γ (K188E) were incubated with 14.5 μg of Fl-GGQ₇RR or 10 μg of GGQ₇RR in 50 μl of reticulocyte buffer for 3 h at 37 °C prior to identifying degradation products by mass spectrometry. The observed masses for all the products listed below varied less than 0.02% from their theoretical masses.

GGQ7RR		Fl-GGQ7RR
Product	% Ion intensity	Product	% Ion intensity
GGQ7R	55	F1-GGQ7R	4
GGQ7	44	F1-GGQ4	20
GGQ6	20	F1-GGQ3	100
GGQ5	33	F1-GGQ2	22
GGQ4	19	F1-GGQ	8
Q6RR	71	Q6R	12
Q3RR	66	Q3	33
Q2RR	38
Q6R	55
Q4R	55
Q3R	22
Q6	37
Q5	41
Q4	100