HEADER HYDROLASE/INHIBITOR 31-DEC-69 8CVT TITLE Human 19S-20S proteasome, state SD2 COMPND MOL_ID: 22; COMPND 2 MOLECULE: 26S proteasome non-ATPase regulatory subunit 3; COMPND 3 CHAIN: V; EXPDTA ELECTRON MICROSCOPY DBREF 8CVT V 1 534 UNP O43242 PSMD3_HUMAN 1 534 SEQRES 1 V 34 ILE ASP ILE TYR SER THR ARG GLU PRO GLN LEU ALA PHE SEQRES 2 V 34 HIS GLN ARG ILE SER PHE CYS LEU ASP ILE HIS ASN MET SEQRES 3 V 34 SER VAL LYS ALA MET ARG PHE PRO ATOM 1 N ILE V 464 145.950 218.475 269.064 1.00213.49 ATOM 2 CA ILE V 464 146.653 219.045 267.879 1.00213.49 ATOM 3 C ILE V 464 148.103 218.562 267.901 1.00213.49 ATOM 4 O ILE V 464 148.557 218.146 268.985 1.00213.49 ATOM 5 CB ILE V 464 146.554 220.583 267.874 1.00213.49 ATOM 6 CG1 ILE V 464 147.008 221.183 269.207 1.00213.49 ATOM 7 CG2 ILE V 464 145.148 221.032 267.507 1.00213.49 ATOM 8 CD1 ILE V 464 146.897 222.688 269.271 1.00213.49 ATOM 9 N ASP V 465 148.763 218.553 266.738 1.00231.93 ATOM 10 CA ASP V 465 150.171 218.081 266.632 1.00231.93 ATOM 11 C ASP V 465 150.193 216.569 266.856 1.00231.93 ATOM 12 O ASP V 465 151.276 216.035 267.153 1.00231.93 ATOM 13 CB ASP V 465 151.128 218.855 267.544 1.00231.93 ATOM 14 CG ASP V 465 151.185 220.342 267.241 1.00231.93 ATOM 15 OD1 ASP V 465 150.575 220.759 266.237 1.00231.93 ATOM 16 OD2 ASP V 465 151.837 221.070 268.013 1.00231.93 ATOM 17 N ILE V 466 149.048 215.909 266.667 1.00227.30 ATOM 18 CA ILE V 466 148.993 214.425 266.795 1.00227.30 ATOM 19 C ILE V 466 149.498 213.884 265.455 1.00227.30 ATOM 20 O ILE V 466 148.716 213.291 264.687 1.00227.30 ATOM 21 CB ILE V 466 147.564 213.985 267.188 1.00227.30 ATOM 22 CG1 ILE V 466 147.410 212.465 267.305 1.00227.30 ATOM 23 CG2 ILE V 466 146.505 214.618 266.293 1.00227.30 ATOM 24 CD1 ILE V 466 148.145 211.862 268.477 1.00227.30 ATOM 25 N TYR V 467 150.783 214.107 265.177 1.00233.06 ATOM 26 CA TYR V 467 151.344 213.726 263.859 1.00233.06 ATOM 27 C TYR V 467 152.349 212.594 264.049 1.00233.06 ATOM 28 O TYR V 467 153.229 212.463 263.180 1.00233.06 ATOM 29 CB TYR V 467 152.068 214.928 263.247 1.00233.06 ATOM 30 CG TYR V 467 151.206 216.050 262.721 1.00233.06 ATOM 31 CD1 TYR V 467 150.030 216.424 263.348 1.00233.06 ATOM 32 CD2 TYR V 467 151.590 216.771 261.603 1.00233.06 ATOM 33 CE1 TYR V 467 149.247 217.462 262.872 1.00233.06 ATOM 34 CE2 TYR V 467 150.820 217.811 261.109 1.00233.06 ATOM 35 CZ TYR V 467 149.645 218.160 261.747 1.00233.06 ATOM 36 OH TYR V 467 148.880 219.184 261.269 1.00233.06 ATOM 37 N SER V 468 152.277 211.868 265.168 1.00204.93 ATOM 38 CA SER V 468 153.317 210.847 265.457 1.00204.93 ATOM 39 C SER V 468 154.650 211.582 265.396 1.00204.93 ATOM 40 O SER V 468 155.599 211.032 264.818 1.00204.93 ATOM 41 CB SER V 468 153.265 209.685 264.513 1.00204.93 ATOM 42 OG SER V 468 154.157 208.661 264.923 1.00204.93 ATOM 43 N THR V 469 154.673 212.812 265.910 1.00206.72 ATOM 44 CA THR V 469 155.904 213.641 265.942 1.00206.72 ATOM 45 C THR V 469 156.316 213.804 267.406 1.00206.72 ATOM 46 O THR V 469 156.206 212.819 268.145 1.00206.72 ATOM 47 CB THR V 469 155.673 215.001 265.276 1.00206.72 ATOM 48 OG1 THR V 469 154.388 215.468 265.687 1.00206.72 ATOM 49 CG2 THR V 469 155.743 214.937 263.767 1.00206.72 ATOM 50 N ARG V 470 156.785 214.993 267.793 1.00220.06 ATOM 51 CA ARG V 470 157.148 215.245 269.214 1.00220.06 ATOM 52 C ARG V 470 155.915 215.125 270.118 1.00220.06 ATOM 53 O ARG V 470 156.025 214.474 271.171 1.00220.06 ATOM 54 CB ARG V 470 157.796 216.622 269.391 1.00220.06 ATOM 55 CG ARG V 470 158.167 216.936 270.833 1.00220.06 ATOM 56 CD ARG V 470 158.972 215.811 271.459 1.00220.06 ATOM 57 NE ARG V 470 159.099 215.871 272.910 1.00220.06 ATOM 58 CZ ARG V 470 158.450 215.094 273.772 1.00220.06 ATOM 59 NH1 ARG V 470 157.615 214.167 273.337 1.00220.06 ATOM 60 NH2 ARG V 470 158.646 215.238 275.070 1.00220.06 ATOM 61 N GLU V 471 154.772 215.686 269.718 1.00233.97 ATOM 62 CA GLU V 471 153.606 215.657 270.645 1.00233.97 ATOM 63 C GLU V 471 153.240 214.196 270.930 1.00233.97 ATOM 64 O GLU V 471 152.993 213.881 272.111 1.00233.97 ATOM 65 CB GLU V 471 152.449 216.501 270.102 1.00233.97 ATOM 66 CG GLU V 471 151.318 216.709 271.094 1.00233.97 ATOM 67 CD GLU V 471 150.078 215.865 270.855 1.00233.97 ATOM 68 OE1 GLU V 471 150.110 215.010 269.951 1.00233.97 ATOM 69 OE2 GLU V 471 149.078 216.070 271.572 1.00233.97 ATOM 70 N PRO V 472 153.203 213.280 269.936 1.00216.19 ATOM 71 CA PRO V 472 152.985 211.854 270.188 1.00216.19 ATOM 72 C PRO V 472 154.284 211.037 270.271 1.00216.19 ATOM 73 O PRO V 472 154.185 209.837 270.113 1.00216.19 ATOM 74 CB PRO V 472 152.166 211.375 268.979 1.00216.19 ATOM 75 CG PRO V 472 151.846 212.640 268.227 1.00216.19 ATOM 76 CD PRO V 472 153.029 213.535 268.511 1.00216.19 ATOM 77 N GLN V 473 155.433 211.668 270.552 1.00213.48 ATOM 78 CA GLN V 473 156.718 210.917 270.536 1.00213.48 ATOM 79 C GLN V 473 156.556 209.747 271.497 1.00213.48 ATOM 80 O GLN V 473 156.992 208.640 271.154 1.00213.48 ATOM 81 CB GLN V 473 157.890 211.777 271.004 1.00213.48 ATOM 82 CG GLN V 473 159.031 210.961 271.598 1.00213.48 ATOM 83 CD GLN V 473 160.202 211.800 272.049 1.00213.48 ATOM 84 OE1 GLN V 473 160.331 212.967 271.692 1.00213.48 ATOM 85 NE2 GLN V 473 161.080 211.201 272.836 1.00213.48 ATOM 86 N LEU V 474 155.950 209.983 272.654 1.00218.85 ATOM 87 CA LEU V 474 155.632 208.842 273.545 1.00218.85 ATOM 88 C LEU V 474 154.598 207.979 272.813 1.00218.85 ATOM 89 O LEU V 474 154.677 206.745 272.928 1.00218.85 ATOM 90 CB LEU V 474 155.069 209.387 274.860 1.00218.85 ATOM 91 CG LEU V 474 154.845 208.351 275.960 1.00218.85 ATOM 92 CD1 LEU V 474 155.882 208.501 277.062 1.00218.85 ATOM 93 CD2 LEU V 474 153.442 208.468 276.535 1.00218.85 ATOM 94 N ALA V 475 153.680 208.605 272.068 1.00213.59 ATOM 95 CA ALA V 475 152.569 207.850 271.440 1.00213.59 ATOM 96 C ALA V 475 153.063 206.793 270.451 1.00213.59 ATOM 97 O ALA V 475 152.548 205.665 270.513 1.00213.59 ATOM 98 CB ALA V 475 151.628 208.813 270.764 1.00213.59 ATOM 99 N PHE V 476 154.021 207.118 269.582 1.00199.92 ATOM 100 CA PHE V 476 154.401 206.100 268.567 1.00199.92 ATOM 101 C PHE V 476 155.676 205.345 268.950 1.00199.92 ATOM 102 O PHE V 476 156.128 204.546 268.123 1.00199.92 ATOM 103 CB PHE V 476 154.338 206.651 267.142 1.00199.92 ATOM 104 CG PHE V 476 153.084 206.245 266.411 1.00199.92 ATOM 105 CD1 PHE V 476 152.720 204.910 266.325 1.00199.92 ATOM 106 CD2 PHE V 476 152.259 207.190 265.822 1.00199.92 ATOM 107 CE1 PHE V 476 151.564 204.529 265.662 1.00199.92 ATOM 108 CE2 PHE V 476 151.104 206.808 265.158 1.00199.92 ATOM 109 CZ PHE V 476 150.758 205.479 265.079 1.00199.92 ATOM 110 N HIS V 477 156.257 205.623 270.119 1.00203.32 ATOM 111 CA HIS V 477 157.418 204.817 270.589 1.00203.32 ATOM 112 C HIS V 477 156.904 203.757 271.562 1.00203.32 ATOM 113 O HIS V 477 157.425 202.627 271.547 1.00203.32 ATOM 114 CB HIS V 477 158.471 205.712 271.250 1.00203.32 ATOM 115 CG HIS V 477 159.323 204.999 272.245 1.00203.32 ATOM 116 ND1 HIS V 477 159.138 205.139 273.606 1.00203.32 ATOM 117 CD2 HIS V 477 160.348 204.136 272.086 1.00203.32 ATOM 118 CE1 HIS V 477 160.017 204.397 274.245 1.00203.32 ATOM 119 NE2 HIS V 477 160.769 203.770 273.335 1.00203.32 ATOM 120 N GLN V 478 155.899 204.117 272.361 1.00211.03 ATOM 121 CA GLN V 478 155.325 203.168 273.347 1.00211.03 ATOM 122 C GLN V 478 154.714 201.991 272.587 1.00211.03 ATOM 123 O GLN V 478 154.827 200.846 273.066 1.00211.03 ATOM 124 CB GLN V 478 154.314 203.876 274.247 1.00211.03 ATOM 125 CG GLN V 478 154.792 204.026 275.684 1.00211.03 ATOM 126 CD GLN V 478 156.127 204.723 275.794 1.00211.03 ATOM 127 OE1 GLN V 478 156.407 205.694 275.095 1.00211.03 ATOM 128 NE2 GLN V 478 156.965 204.236 276.695 1.00211.03 ATOM 129 N ARG V 479 154.100 202.270 271.439 1.00201.81 ATOM 130 CA ARG V 479 153.452 201.193 270.655 1.00201.81 ATOM 131 C ARG V 479 154.518 200.167 270.263 1.00201.81 ATOM 132 O ARG V 479 154.245 198.959 270.381 1.00201.81 ATOM 133 CB ARG V 479 152.840 201.793 269.387 1.00201.81 ATOM 134 CG ARG V 479 151.379 201.432 269.163 1.00201.81 ATOM 135 CD ARG V 479 150.449 202.253 270.036 1.00201.81 ATOM 136 NE ARG V 479 150.593 203.683 269.801 1.00201.81 ATOM 137 CZ ARG V 479 149.877 204.384 268.929 1.00201.81 ATOM 138 NH1 ARG V 479 148.953 203.787 268.196 1.00201.81 ATOM 139 NH2 ARG V 479 150.087 205.681 268.793 1.00201.81 ATOM 140 N ILE V 480 155.690 200.637 269.828 1.00197.51 ATOM 141 CA ILE V 480 156.791 199.713 269.428 1.00197.51 ATOM 142 C ILE V 480 157.263 198.934 270.653 1.00197.51 ATOM 143 O ILE V 480 157.565 197.742 270.494 1.00197.51 ATOM 144 CB ILE V 480 157.945 200.430 268.698 1.00197.51 ATOM 145 CG1 ILE V 480 159.246 200.462 269.508 1.00197.51 ATOM 146 CG2 ILE V 480 157.523 201.815 268.250 1.00197.51 ATOM 147 CD1 ILE V 480 160.203 199.332 269.196 1.00197.51 ATOM 148 N SER V 481 157.299 199.564 271.828 1.00206.40 ATOM 149 CA SER V 481 157.884 198.853 272.992 1.00206.40 ATOM 150 C SER V 481 157.100 197.562 273.224 1.00206.40 ATOM 151 O SER V 481 157.740 196.536 273.466 1.00206.40 ATOM 152 CB SER V 481 157.915 199.712 274.225 1.00206.40 ATOM 153 OG SER V 481 156.642 199.749 274.849 1.00206.40 ATOM 154 N PHE V 482 155.772 197.608 273.110 1.00205.53 ATOM 155 CA PHE V 482 154.974 196.391 273.403 1.00205.53 ATOM 156 C PHE V 482 155.322 195.269 272.414 1.00205.53 ATOM 157 O PHE V 482 155.538 194.128 272.863 1.00205.53 ATOM 158 CB PHE V 482 153.482 196.730 273.373 1.00205.53 ATOM 159 CG PHE V 482 152.567 195.541 273.233 1.00205.53 ATOM 160 CD1 PHE V 482 152.389 194.652 274.281 1.00205.53 ATOM 161 CD2 PHE V 482 151.877 195.312 272.053 1.00205.53 ATOM 162 CE1 PHE V 482 151.549 193.558 274.149 1.00205.53 ATOM 163 CE2 PHE V 482 151.036 194.218 271.923 1.00205.53 ATOM 164 CZ PHE V 482 150.873 193.343 272.971 1.00205.53 ATOM 165 N CYS V 483 155.387 195.579 271.115 1.00203.08 ATOM 166 CA CYS V 483 155.664 194.540 270.086 1.00203.08 ATOM 167 C CYS V 483 157.087 194.019 270.276 1.00203.08 ATOM 168 O CYS V 483 157.302 192.795 270.172 1.00203.08 ATOM 169 CB CYS V 483 155.514 195.122 268.689 1.00203.08 ATOM 170 SG CYS V 483 153.936 195.974 268.434 1.00203.08 ATOM 171 N LEU V 484 158.019 194.927 270.545 1.00216.03 ATOM 172 CA LEU V 484 159.433 194.547 270.785 1.00216.03 ATOM 173 C LEU V 484 159.499 193.687 272.052 1.00216.03 ATOM 174 O LEU V 484 160.346 192.785 272.106 1.00216.03 ATOM 175 CB LEU V 484 160.233 195.847 270.880 1.00216.03 ATOM 176 CG LEU V 484 161.354 195.897 271.908 1.00216.03 ATOM 177 CD1 LEU V 484 162.651 195.389 271.297 1.00216.03 ATOM 178 CD2 LEU V 484 161.517 197.324 272.402 1.00216.03 ATOM 179 N ASP V 485 158.639 193.964 273.036 1.00219.47 ATOM 180 CA ASP V 485 158.584 193.150 274.282 1.00219.47 ATOM 181 C ASP V 485 158.180 191.712 273.942 1.00219.47 ATOM 182 O ASP V 485 158.611 190.797 274.668 1.00219.47 ATOM 183 CB ASP V 485 157.658 193.775 275.328 1.00219.47 ATOM 184 CG ASP V 485 158.259 194.995 276.005 1.00219.47 ATOM 185 OD1 ASP V 485 159.457 195.259 275.778 1.00219.47 ATOM 186 OD2 ASP V 485 157.521 195.677 276.742 1.00219.47 ATOM 187 N ILE V 486 157.405 191.515 272.871 1.00202.32 ATOM 188 CA ILE V 486 156.917 190.153 272.493 1.00202.32 ATOM 189 C ILE V 486 158.094 189.350 271.935 1.00202.32 ATOM 190 O ILE V 486 157.890 188.172 271.601 1.00202.32 ATOM 191 CB ILE V 486 155.725 190.202 271.520 1.00202.32 ATOM 192 CG1 ILE V 486 154.561 191.016 272.091 1.00202.32 ATOM 193 CG2 ILE V 486 155.292 188.793 271.146 1.00202.32 ATOM 194 CD1 ILE V 486 153.978 190.444 273.361 1.00202.32 ATOM 195 N HIS V 487 159.274 189.965 271.846 1.00211.59 ATOM 196 CA HIS V 487 160.490 189.231 271.408 1.00211.59 ATOM 197 C HIS V 487 160.771 188.138 272.440 1.00211.59 ATOM 198 O HIS V 487 161.692 187.334 272.216 1.00211.59 ATOM 199 CB HIS V 487 161.698 190.166 271.310 1.00211.59 ATOM 200 CG HIS V 487 162.991 189.488 271.615 1.00211.59 ATOM 201 ND1 HIS V 487 163.666 188.729 270.679 1.00211.59 ATOM 202 CD2 HIS V 487 163.730 189.443 272.744 1.00211.59 ATOM 203 CE1 HIS V 487 164.769 188.249 271.218 1.00211.59 ATOM 204 NE2 HIS V 487 164.830 188.672 272.485 1.00211.59 ATOM 205 N ASN V 488 160.027 188.143 273.546 1.00215.25 ATOM 206 CA ASN V 488 160.193 187.103 274.597 1.00215.25 ATOM 207 C ASN V 488 159.925 185.722 273.990 1.00215.25 ATOM 208 O ASN V 488 160.470 184.740 274.516 1.00215.25 ATOM 209 CB ASN V 488 159.260 187.345 275.783 1.00215.25 ATOM 210 CG ASN V 488 159.636 188.564 276.598 1.00215.25 ATOM 211 OD1 ASN V 488 158.865 189.011 277.443 1.00215.25 ATOM 212 ND2 ASN V 488 160.817 189.108 276.353 1.00215.25 ATOM 213 N MET V 489 159.120 185.652 272.927 1.00216.31 ATOM 214 CA MET V 489 158.767 184.349 272.310 1.00216.31 ATOM 215 C MET V 489 160.050 183.647 271.863 1.00216.31 ATOM 216 O MET V 489 160.104 182.413 271.966 1.00216.31 ATOM 217 CB MET V 489 157.865 184.542 271.090 1.00216.31 ATOM 218 CG MET V 489 156.388 184.480 271.408 1.00216.31 ATOM 219 SD MET V 489 155.875 185.760 272.576 1.00216.31 ATOM 220 CE MET V 489 154.115 185.437 272.661 1.00216.31 ATOM 221 N SER V 490 161.030 184.402 271.366 1.00202.17 ATOM 222 CA SER V 490 162.323 183.789 270.971 1.00202.17 ATOM 223 C SER V 490 163.005 183.169 272.191 1.00202.17 ATOM 224 O SER V 490 163.611 182.103 272.047 1.00202.17 ATOM 225 CB SER V 490 163.239 184.762 270.286 1.00202.17 ATOM 226 OG SER V 490 163.701 185.748 271.196 1.00202.17 ATOM 227 N VAL V 491 162.959 183.837 273.339 1.00211.04 ATOM 228 CA VAL V 491 163.547 183.215 274.560 1.00211.04 ATOM 229 C VAL V 491 162.742 181.983 274.990 1.00211.04 ATOM 230 O VAL V 491 163.369 180.935 275.229 1.00211.04 ATOM 231 CB VAL V 491 163.658 184.244 275.701 1.00211.04 ATOM 232 CG1 VAL V 491 164.501 183.721 276.853 1.00211.04 ATOM 233 CG2 VAL V 491 164.203 185.573 275.202 1.00211.04 ATOM 234 N LYS V 492 161.409 182.075 275.021 1.00204.72 ATOM 235 CA LYS V 492 160.602 180.952 275.573 1.00204.72 ATOM 236 C LYS V 492 160.767 179.682 274.737 1.00204.72 ATOM 237 O LYS V 492 161.043 178.618 275.325 1.00204.72 ATOM 238 CB LYS V 492 159.118 181.332 275.586 1.00204.72 ATOM 239 CG LYS V 492 158.747 182.484 276.508 1.00204.72 ATOM 240 CD LYS V 492 158.825 182.116 277.972 1.00204.72 ATOM 241 CE LYS V 492 157.887 180.988 278.343 1.00204.72 ATOM 242 NZ LYS V 492 158.008 180.619 279.773 1.00204.72 ATOM 243 N ALA V 493 160.637 179.799 273.417 1.00208.18 ATOM 244 CA ALA V 493 160.718 178.597 272.560 1.00208.18 ATOM 245 C ALA V 493 162.142 178.039 272.603 1.00208.18 ATOM 246 O ALA V 493 162.291 176.811 272.605 1.00208.18 ATOM 247 CB ALA V 493 160.191 178.854 271.172 1.00208.18 ATOM 248 N MET V 494 163.142 178.917 272.675 1.00211.72 ATOM 249 CA MET V 494 164.558 178.471 272.715 1.00211.72 ATOM 250 C MET V 494 164.765 177.599 273.956 1.00211.72 ATOM 251 O MET V 494 165.597 176.681 273.893 1.00211.72 ATOM 252 CB MET V 494 165.501 179.673 272.788 1.00211.72 ATOM 253 CG MET V 494 166.947 179.338 272.487 1.00211.72 ATOM 254 SD MET V 494 168.018 180.794 272.585 1.00211.72 ATOM 255 CE MET V 494 169.617 180.044 272.286 1.00211.72 ATOM 256 N ARG V 495 164.096 177.928 275.062 1.00207.43 ATOM 257 CA ARG V 495 164.203 177.132 276.318 1.00207.43 ATOM 258 C ARG V 495 163.639 175.714 276.154 1.00207.43 ATOM 259 O ARG V 495 164.201 174.800 276.785 1.00207.43 ATOM 260 CB ARG V 495 163.522 177.860 277.481 1.00207.43 ATOM 261 CG ARG V 495 164.192 179.171 277.862 1.00207.43 ATOM 262 CD ARG V 495 165.643 178.979 278.261 1.00207.43 ATOM 263 NE ARG V 495 166.486 180.065 277.780 1.00207.43 ATOM 264 CZ ARG V 495 167.257 179.998 276.701 1.00207.43 ATOM 265 NH1 ARG V 495 167.312 178.882 275.993 1.00207.43 ATOM 266 NH2 ARG V 495 167.984 181.041 276.342 1.00207.43 ATOM 267 N PHE V 496 162.587 175.520 275.350 1.00217.24 ATOM 268 CA PHE V 496 161.902 174.195 275.280 1.00217.24 ATOM 269 C PHE V 496 162.773 173.002 274.845 1.00217.24 ATOM 270 O PHE V 496 162.578 171.947 275.475 1.00217.24 ATOM 271 CB PHE V 496 160.628 174.286 274.438 1.00217.24 ATOM 272 CG PHE V 496 159.536 175.105 275.077 1.00217.24 ATOM 273 CD1 PHE V 496 159.054 174.783 276.335 1.00217.24 ATOM 274 CD2 PHE V 496 158.991 176.197 274.424 1.00217.24 ATOM 275 CE1 PHE V 496 158.054 175.537 276.926 1.00217.24 ATOM 276 CE2 PHE V 496 157.995 176.954 275.018 1.00217.24 ATOM 277 CZ PHE V 496 157.525 176.621 276.266 1.00217.24 ATOM 278 N PRO V 497 163.674 173.048 273.833 1.00205.94 ATOM 279 CA PRO V 497 164.425 171.860 273.401 1.00205.94 ATOM 280 C PRO V 497 164.740 170.836 274.501 1.00205.94 ATOM 281 O PRO V 497 164.861 169.675 274.151 1.00205.94 ATOM 282 CB PRO V 497 165.718 172.482 272.865 1.00205.94 ATOM 283 CG PRO V 497 165.233 173.736 272.182 1.00205.94 ATOM 284 CD PRO V 497 164.055 174.201 273.016 1.00205.94 TER