Table 1. List of the identified proteins by mass spectrometry after Ufm1_STrEPtag affinity purification.

Frag-ment	protein name	Swiss ProtAccession nr	Mw (kDa)	# peptides seq/unique		sequence coverage %	Function
1	UFM1; Ubiquitin fold modifier 1	P61961	9	2	2	31.8	ER stress-induced apoptosis (this paper)
2	UFC1; Ufm1-conjugating enzyme 1	Q9CR09	20	3	2	10.8	E2 enzyme of UFM1 (Komatsu et al, 2004)
3	UFC1; Ufm1-conjugating enzyme 1	Q9CR09	20	2	1	6	E2 enzyme of UFM1 (Komatsu et al, 2004)
4	UFBP1; Ufm1 binding protein containing a PCI domain	Q80WW9	36	4	3	13.3	ERAD/ER stress-induced apoptosis, target of UFM1 (Tatsumi et al, 2010; this paper)
5	UBA5; Ubiquitin-like modifier-activating enzyme 5	Q8VE47	45	2	2	4.7	E1 enzyme of Ufm1 (Komatsu et al, 2004) [4]
6	UBA5; Ubiquitin-like modifier-activating enzyme 5	Q8VE47	45	2	2	5.2	E1 enzyme of UFM1 (Komatsu et al, 2004)
	CDK5RAP3; CDK5 regulatory subunit-associated protein 3	Q99LM2	57	4	3	6.4	tumor suppressor (Wang et al, 2007); substrate of Ufm1 (this paper)
7	HSPA5/BiP; 78 kDa glucose-regulated protein precursor	P20029	72	3	3	4.7	ER stress, chaperone (Ma, Hendershot, 2004)
	HSPA8; Heat shock 70 kDa protein 8	P63017	71	5	5	8	chaperone (Zimmerman, 1998)
8	Ufl1; UFM1 ligation protein	Q8CCJ3	100	7	7	9.7	E3 enzyme of UFM1 (Tatsumi et al., 2010, this paper)
9	PCX;Pyruvate carboxylase	Q05920	130	12	11	12.3	anaplerosis//cataplerosis (Fransson et al, 2006)