Table 1.

Identification of proteins by LC-MS/MS in co-IP experiments

Proteina	Peptide coverageb
	STT3Bc		STT3Ac	MagT1-V5c
	cRMd	HeLad	cRMd	HeLad
STT3B	13	9	0	18
STT3A	0	0	3	0
Ribophorin I	75	42	47	39
Ribophorin II	58	37	13	44
OST48	53	44	43	40
MagT1	17	6	0	19
DAD1	35	19	19	19
Malectin	36	13	9	40
Calnexine	10	0	0	22
Calreticuline	0	0	0	34
Sec61α	0	0	0	0

^aOST subunits that were not detected in any sample include TUSC3, OST4, DC2, and KPC2. OST4, DC2, and KPC2 are low molecular weight hydrophobic membrane proteins, so they may not have been detected due to the limited number of tryptic fragments. TUSC3 is not expressed in HeLa cells.

^bPeptide coverage for the protein recognized by the precipitating antibody is low because the beads were eluted with a mixed-micelle immunoprecipitation wash buffer.

^cAntibody.

^dMembrane source. Digitonin solubilized HeLa cells or cRM were used for co-IP assays.

^eThe presence of calnexin and calreticulin in co-IP samples could not be verified by protein immunoblotting.