Table 1.

Cross-links detected in Hsp21

MS/MS spectra for all detected cross-links and MS spectra for detected hybrid crosslinks are provided in Supplemental Information 5.

Lys A	Lys B	Peptide A	Peptide B	Distance Cα—Cαa	Distance within dimer Cα–Cαa	Distance within the disc Cα–Cαa	Distance between discs Cα–Cαa	Detected in subunit or dimer band or ISb	Detected as hybrid cross-link in ISc	Intra- or intersubunitd
				Å	Å	Å	Å
1	18	MQDQR	ENSIDVVQQGQQKGNQGSSVEK					IS	Y	4
1	18	MQDQR	ENSIDVVQQGQQKGNQGSSVEKRPQQR					IS	Y	4
1	27	MQDQR	GNQGSSVEKRPQQR					IG-M, IS	Y	2
1	106	MQDQR	MRFDMPGLSKEDVK					IS	N	1
1	110	MQDQR	EDVKISVEDNVLVIK					IG-D	ND	3
1	125	MQDQR	GEQKKEDSDDSWSGR					IG-M, IG-D, IS	Y	2
1	126	MQDQR	KEDSDDSWSGR					IG-M, IS	Y	2
1	157	MQDQR	IKAELK					IG-M, IS	Y	2
1	161	MQDQR	AELKNGVLFITIPK					IG-M, IG-D, IS	Y	2
1	173	MQDQR	TKVER					IG-M, IS	Y	2
27	121	GNQGSSVEKRPQQR	ISVEDNVLVIKGEQK					IS	Y*	4
89	125	APWDIKEEEHEIK	GEQKKEDSDDSWSGR	32.9	20.4	29.0	52.0	IG-M	ND	5
89	126	APWDIKEEEHEIKMR	KEDSDDSWSGR	35.3	18.9	32.6	49.2	IG-M, IS	Y*	5
89	173	APWDIKEEEHEIK	TKVER	11.2	56.4	35.1	32.1	IS	N	1
96	126	APWDIKEEEHEIKMR	KEDSDDSWSGR	28.7	15.9	36.6	46.2	IG-M	ND	5
106	161	FDMPGLSKEDVK	AELKNGVLFITIPK	9.3	16.0	48.3	58.3	IG-M, IS	Y	2
121	126	ISVEDNVLVIKGEQK	KEDSDDSWSGR	17.0	27.0	29.6	35.1	IG-M	N	1
121	173	ISVEDNVLVIKGEQK	TKVER	27.8	45.8	24.0	50.6	IS	Y*	5
125	161	GEQKKEDSDDSWSGR	AELKNGVLFITIPK	17.2	16.1	45.1	52.0	IG-D	ND	3
126	157	KEDSDDSWSGR	IKAELKNGVLFITIPK	26.9	23.5	47.0	46.2	IG-M	ND	5
126	161	KEDSDDSWSGR	AELKNGVLFITIPK	18.4	16.7	48.1	51.4	IG-D, IS	Y*	4
153	157	LQLPDNCEKDK	IKAELK	9.3	44.8	33.6	58.6	IG-M	ND	5
157	173	IKAELK	TKVER	16.7	50.6	26.8	46.2	IG-M, IG-D	ND	5

^a Calculated Cα–Cα distances for cross-linked lysines according to the Hsp21 structural model (within one subunit, between subunits within a dimer, between adjacent subunits in the same disc, and between the discs).

^b Samples were analyzed to detect cross-links either after SDS-PAGE and in-gel digestion of bands corresponding to a cross-linked monomeric (IG-M) or dimeric (IG-D) subunit or without prior SDS-PAGE fractionation by in-solution digestion (IS). Cross-links detected in a band corresponding to a monomeric subunit are considered to be intrasubunit, not excluding the possibility that it can also be intersubunit.

^c Sample was a 1:1 mixture of non-labeled and ¹⁵N-labeled Hsp21 subjected to in-solution digestion and analyzed for hybrid cross-links (i.e. cross-links between one unlabeled (¹⁴N) and one ¹⁵N-labeled peptide). Cross-links detected as hybrid cross-links (Y = yes, and Y* refers to an experiment where Hsp21 was mixed with Hsp21V^181A) are considered to be intersubunit and are marked in boldface type. Also noted is if the cross-link was detected only as ¹⁴N-¹⁴N or ¹⁵N-¹⁵N (i.e. not as hybrid cross-links (n = no)) or not detected (ND).

^d The following classifications are used concerning whether they are intra- or intersubunit: 1 = intrasubunit, 2 = intra- and intersubunit, 3 = intra- or intersubunit, 4 = inter- and possibly intrasubunit, 5 = intra- and possibly intersubunit.