1. Electronic Supplementary Material for the manuscript entitled: Effective selenium detoxification in the seed proteins of a hyperaccumulator plant: the analysis of selenium containing proteins of monkeypot nut ( Lecythis minor ) seeds by A. Németh and M. Dernovics, published in Journal of Biological Inorganic Chemistry Table S 2 Instrumental parameters of the HPLC-ESI-QTOF-MS set-up. 6530 Accurate Mass QTOF LC-MS (Agilent) ESI sourceDual ESI (Agilent) Operational modePositive Precursor ion isolation in MS/MS modemedium (4 m/z) Mass accuracy< 2 ppm Mass resolution> 10000 Detection frequency 4 GHz Fragmentor voltage150 V/-150 V Curtain voltage65 V/ -65 V Drying gas13 L/min Capillary voltage800 V Nebulizer pressure40 psig Gas temperature325 ºC Data analysis softwareMass Hunter Acquisition B.02.01 with SP3 Mass Hunter Qualitative Analysis B.03.01 with SP3 Table S 1 Chromatographic parameters applied. ColumnXDB C18, 4.6 mm x 100 mm x 5 µm Injection volume (µL)10 Flow rate (mL min -1 )0.35 Buffer A0.1% formic acid in water Buffer Bacetonitrile with 0.1% formic acid Gradient program0-210% B 4up to 20% B 10up to 45% B 15up to 100% B 20100% B 22down to 10% B

2. Table S 4. Protein database search identification results. The coverage was calculated by the sotware based on the sequence of the precursor protein. In the case of 2S albumin and 2S sulfur-rich proteins, the signal and propeptides are removed during the maturation of the proteines. The revised coverages were calculated based on the sequence of the mature proteins. Methionine coverage is the coverage of methionine containing peptides. Se-containing peptides are highlighted. Accession number DescriptionOrganism Software coverage Calculated coverage Methionine coverage Peptides Sequencem/zzMassMass errorStartEnd Q84ND211S globulinB. excelsa313225 VIRPP 291.19212581.37680.03260264 VQIVDHR 289.4993866.48222.24360366 HFFLAGNIQR 401.550631202.6374.78185194 CAGVAALR 409.22062817.43381.156471 LYYVTGR 500.26542999.52342.279097 NGETVFDDNLR 583.277821165.54820367376 VQHTASDLNQLDQNPR 612.637731835.89830.47169184 NTIRPQGLLLPVYTNAPK 665.717531995.13770.277289 KGDIIAIPAGVALW 712.418621423.82980.62142155 GILGVLMPGCPETF 745.873721490.741.3298111 GILGVLBPGCPETF 769.845721538.6840.9798111 LTTVNSLKVPILTF 773.464321545.92122.46310323 FIQNIDNPAEDFYNPR 1012.482322023.95723.18290306 VPILTFLQL 1043.649522086.29160.39318326 B6EU542S albuminB. excelsa1829 GEQMR 310.64462620.28184.78112116 CEGLR 317.65192634.29641.839397 EMQPR 330.65942660.31142.77107111 GEQBR 334.6152668.22265.61112116 EBQPR 354.63152708.25562.96107111 QQMLSH 372.17722743.3474.534651 pyro-QQBLSH 396.15212791.29682.434651 CNLSPQR 437.71312874.41881.18129135 MAENLPSR 459.2292917.45060.15121128 BAENLPSR 483.20052965.39361.73121128 P04403 2S sulfur-rich storage protein 1 B. excelsa1532 GEQMR 310.64462620.28180.26113117 CEGLR 317.65192634.29641.839498 EMQPR 330.65942660.31142.77108112 GEQBR 334.6152668.22265.61113117 EBQPR 354.63152708.25562.96108112 QQMLSH 372.17722743.3474.534752 AENLPSR 393.70752786.40763.04123129 pyro-QQBLSH 396.15212791.29682.434752 MQQEEMQPR 588.760621176.51380.3104112 BQQEEMQPR 612.731921224.45641.29104112 BQQEEBQPR 636.704721272.4020.38104112 QQBLSH 774.26851 0.144752 P0C8Y8 2S sulfur-rich storage protein 2 B. excelsa51519 MYLR 291.65742582.30743.116265 BYLR 315.62892630.25041.036265 CEGLR 317.65192634.29644.75103107 CNLSPQR 437.71212874.41681.18138144 Table S 3. Database search and protein validation settings. Database search settings Name and version of the programPeptideShaker1-0-23-0 EnzymeTrypsin Fixed modificationCarbamidomethyl cysteine Variable modifications Phosphorylation of serine or tyrosine Oxidation of methionine Selenomethionine Selenocysteine Precursor mass tolerance10 ppm Fragment ion typesb and y Maximum missed cleavages2 Fragment mass tolerance0.05 mDa Precursor charge2-3 Validation settings Validated hits8 Confidence95% Lowest confidence of validated results100% FDR1 FNR1

3. x10 2 0 1.2 2.4 20030040050060070080090010001100120013001400 y2y2 y1y1 y4y4 y5y5 y7y7 y8y8 m/z Intensity, cps y 12 GVLM P 938.3631 1051.25981150.5272 1207.5487 683.4041552.3636439.2795 340.2111 I L 1320.6328 1433.7168 283.1896 1170.1055 C*PE T F 267.1298 493.2352 653.2491 1324.65201223.60431094.5617 997.5089 G 710.2815 807.3180 837.4783 780.4568 396.1766 G 166.0863 57.0215 x10 2 0 1 2 2003004005006007008009001000 m/z Intensity. cps y2y2 y1y1 y4y4 y5y5 y7y7 y8y8 y9y9 y 5’ y 7’ y 6’ GVLB P 986.3192 1099.42281198.4717 1255.4932 731.3486552.3636439.2795 340.2111 I L 1368.5773 1481.6613 283.1896 170.1055 CPE T F 267.1298 493.2352 653.2491 1372.59651271.54881142.5062 1045.4535 G 710.2815 807.3180 885.4228 828.4013 396.1766 G 166.0863 57.0215 GVLM P 986.3192 1099.42281198.4717 1255.4932 683.4041552.3636439.2795 340.2111 I L 1368.5773 1481.6613 283.1896 170.1055 SeCPE T F 267.1298 493.2352 701.1545 1372.59651271.54881142.5062 1045.4535 G 758.1760 855.2287 837.4783 780.4568 396.1766 G 166.0863 57.0215 y7y7 y 5’ y 7’ y 6’ m/z Intensity, cps x10 2 0 0.8 1.6 807.31804 733.05634 700725750775800825850 (‘) Figure S 1. The MS-MS spectra and the identification details of the peptide GILGVLMPGCPETF and its selenium analogue. While the selenopeptide was identified by the search engines as a Sec containing peptide, the manual checking of the MS-MS spectra revealed the absence of Sec containing fragments (y5’, y6’, y7’). In the peptide sequence C* corresponds to carbamydomethyl- cysteine, B denotes to selenomethionine and Sec represents selenocysteine.

4. m/z Intensity, cps x10 3 0 4 8 100200300400500600700 BSK 147.1130 234.1449 576.0425 489.0105 MB 413.1325 592.1152 310.0255 131.0405 BSK 147.1130 234.1449 576.0425 489.0105 BM 413.1307 544.1713 310.0255 178.9852 MSK 147.1131 234.1451 576.0425 489.0105 BB 365.1855 544.1716 357.9704 178.9857 y1y1 y2y2 y3y3 y4y4 y 2’ y 3’ y 4’ y 4’’ y 2’’ 0 0,5 1 100200300400500600 x10 4 m/z Intensity, cps MSK 147.1130 234.1451 528.0981 441.0665 BM 365.1829 496.2265 310.0255 178.9857 MSK 147.1130 234.1451 528.0981 441.0665 MB 365.1829 544.1716 310.0255 131.0405 BSK 147.1131 234.1451 528.0981 441.0665 MM 413.1301 544.1716 262.0812 131.0405 y1y1 y3y3 y4y4 y 2’’ y 3’ y 3’’ y 4’ y 4’’ b2b2 y2y2 y 2’ y 2’’ Figure S 2. MS-MS spectra and details of de novo sequencing of selenopeptides. x10 4 0 0,7 1,4 100200300400500600 m/z Intensity, cps MSK 147.1126 234.1452 480.1535 393.1215 MM 365.1860 496.2284 263.0893 131.0405 y1y1 y2y2 y3y3 y4y4

5. m/z Intensity, cps x10 3 0 2.5 5 50100150200250300350400450500550600650700750800850900950 y1y1 y2y2 y3y3 y4y4 SFB 585.1870 732.2584 363.1431 216.0746 E 819.2912 129.0426 GSR 175.1192 262.1512 773.2136 686.1815 S 319.1725 406.2034 629.1601 542.1285 y5y5 y6y6 x10 4 0 0,5 1 50100150200250300350400450500550600650700750800850900950 m/z Intensity, cps y1y1 y2y2 y3y3 y4y4 y5y5 y6y6 GKN 750.3392 878.4336 332.1849 204.0899 F 935.4249 147.0684 CAM 306.1577 377.1963 776.3642 705.3269 V 537.2294 636.2913 545.2962 446.2278 R 175.1183 907.4045 y7y7 y8y8 x10 3 0 1,2 2,4 5010015020025030035040045050055060065070075080085090095010001050 m/z Intensity, cps y1y1 y2y2 y3y3 y4y4 y5y5 y6y6 GKN 798.2741 926.3781 332.1849 204.0899 F 983.3703 147.0684 CAB 354.1755 425.1411 776.3642 705.3269 V 585.1718 684.2458 545.2962 446.2278 R 175.1191 955.3490 y7y7 y8y8 x10 4 0 0,5 1 100200300400500600700800900 m/z Intensity, cps y1y1 y2y2 y3y3 y4y4 SFM 537.2441 684.3134 363.1431 216.0746 E 771.3455 129.0426 GSR 175.1192 262.1512 725.2691 638.2374 S 319.1725 406.2027 581.2156 494.1835 y5y5 y6y6 y7y7

6. MGM 933.4095 990.4787 367.0815 310.0255 B 1121.5171 178.9855 ENP 488.2464 602.2893 812.2101 698.1246 A 731.3882 802.45233 569.1246 498.0874 E 391.1936 909.2629 S 262.1510 1038.4432 R 175.1191 1125.3371 BGM 933.4095 990.4787 367.0815 310.0255 M 1169.5054 131.0405 ENP 488.2464 602.2893 812.2101 698.1246 A 731.3882 802.45233 569.1246 498.0874 E 391.1936 909.2629 S 262.1510 1038.4432 R 175.1191 1125.3371 MGB 981.3542 1038.4432 319.1025 262.0812 M 1121.5171 131.0405 ENP 488.2464 602.2893 812.2101 698.1246 A 731.3882 802.45233 569.1246 498.0874 E 391.1936 909.2629 S 262.1510 1038.4432 R 175.1191 1125.3371 x10 2 0 1.3 2.6 1001502002503003504004505005506006507007508008509009501000105011001150120012501300 m/z Intensity, cps y1y1 y2y2 y3y3 y5y5 y6y6 y7y7 y8y8 y 10 y4y4 y 8’ y 10’’ y 9’’ y9y9 y 9’ y 10’ x10 3 0 2 4 100150200250300350400450500550600650700750800850900950100010501100 m/z Intensity, cps ENAM M 605.2911 676.3329790.3750 919.4025 877.4117746.3712675.3341 561.2911 IY 1082.4766 1195.5610 432.2485 269.1823 P R 175.1193 270.1820 1176.5423 A 343.2074 474.2419 1079.4892 1008.4521 R 156.1011 y1y1 y2y2 y3y3 y4y4 y5y5 y6y6 y7y7 y8y8 y9y9 y 10 m/z Intensity, cps x10 2 0 2.5 5 100150200250300350400450500550600650700750800850900950100010501100115012001250130013501400 ENAB M 653.2148 724.3034837.3211 967.3614 925.3562746.3712675.3341 561.2911 IY 1130.4279 1243.5041 432.2485 269.1823 P R 175.1193 270.1820 1224.4873 A 343.1984 474.2369 1127.4345 1056.3972 R 156.1011 y1y1 y2y2 y3y3 y4y4 y5y5 y6y6 y7y7 y8y8 y9y9 y 10 x10 2 0 2.5 5 100150200250300350400450500550600650700750800850900950100010501100115012001250 m/z Intensity, cps y1y1 y2y2 y4y4 y5y5 y6y6 y7y7 y8y8 MGM 933.4817 990.4955 319.1088 262.0814 M 1121.5171 131.0405 ENP 488.2464 602.3191 764.2656 650.2227 A 731.3963 802.4511 521.1948 450.1429 E 391.1936 861.3184 S 262.1512 990.3612 R 175.1191 1077.3932 y9y9 y 10