Table S5.

Peptides and modification sites detected by XF-MS, and the ratio(s) of hydroxyl radical reactivity for OCPR versus OCPO

Seq. no.*Peptide sequenceSite of modificationRatio “R“ of hydroxyl radical reactivity kOCPR/kOCPO§
2–9PFTIDSARP2, F3 (+16 Da)0.74 ± 0.15
A8, R9 (+16 Da)1.85 ± 0.39
10–27GIFPNTLAADVVPATIARResidues 13–22 (+16 Da)1.93 ± 0.25
28–49FSQLNAEDQLALIWFAYLEMGKW41 (+48 Da)0.35 ± 0.05
W41, F42, Y44, M47 (+16 Da)0.47 ± 0.09
M47 (+16 Da)0.76 ± 0.16
50–69TLTIAAPGAASMQLAENALKA54, A55, P56 (+16 Da)0.76 ± 0.09
M61 (+16 Da)1.06 ± 0.22
70–89EIQAMGPLQQTQAMCDLANRM74 (+16 Da)0.69 ± 0.13
M74P76M83 (+16 Da)0.67 ± 0.02
97–106TYASWSPNIKY98W101P103 (+16 and +32 Da)1.95 ± 0.30
107–112LGFWYF109W110Y111 (+16 and +32 Da)0.90 ± 0.13
113–155LGELMEQGFVAPIPAGYQLSANANAVLATIQGLESGQQITVLRM117 (+16 Da)0.69 ± 0.13
119–146QGFVAPIPAGYQLSANANAVLATIQGLEF121,P124,P126 (+16 Da)#0.17 ± 0.05
147–160SGQQITVLRNAVVDR155, N156 (+16 Da)10.11 ± 3.96
156–167NAVVDMGFTAGKM161 (+16 Da)0.68 ± 0.12
F163 (+16 Da)0.78 ± 0.46
K167 (+16 Da)0.70 ± 0.21
172–185IAEPVVPPQDTASRP175P178P179R185 (+16 Da)0.58 ± 0.06
192–215GVTNATVLNYMDNLNANDFDTLIEM202 (+16 Da)1.1 ± 0.18
Residues 119–215 (+16 Da)#0.89 ± 0.08
221–235GALQPPFQRPIVGKEResidues 226–231 (+16 Da)#0.58 ± 0.07
243–249EECQNLKNo modification||
255–268GVTEPAEDGFTQIKP259, F264, K268 (+16 Da)1.02 ± 0.11
273–289VQTPWFGGNVGMNIAWRP276, W277, F278 (+32 Da)2.02 ± 0.23
M284 (+16 Da)1.54 ± 0.17
290–297FLLNPEGKF190 (+16 Da)2.16 ± 0.33
L291, L292 (+16 Da)0.59 ± 0.05
P294 (+16 Da)0.58 ± 0.11
298–310IFFVAIDLLASPKI298, F299 (+16 Da)1.21 ± 0.27
V301, A302, I303 (+16 Da)2.08 ± 0.30
P309, K310 (+16 Da)0.46 ± 0.07
  • * The 94% sequence coverage was obtained from the bottom-up LC-electrospray ionization (ESI)-MS analysis of OCPO and OCPR using trypsin and Glu-C digestion.

  • Sequences of digested fragments identified by mass spectrometry analysis described in SI Methods.

  • Positions of modified residues identified by mass spectrometry analysis described in SI Methods.

  • § The ratio (R) of hydroxyl radical reactivity rate between OCPO and OCPR from three independent measurements. The rate constants (k s−1) were estimated by using a nonlinear fit of hydroxyl radical modification data to a first order decay as described in SI Methods. R is a quantitative measure of the change in the solvent accessibility.

  • Mass shift due to side chain modification is show within the parentheses.

  • # Side chain modification at multiple residues within the specified sequence number.

  • || No ratio of hydroxyl radical reactivity.