HEADER PEPTIDE BINDING PROTEIN 31-DEC-69 6MAA TITLE WFIKKN2 Follistatin Domain COMPND MOL_ID: 1; COMPND 2 MOLECULE: WAP, Kazal, immunoglobulin, Kunitz and NTR COMPND 3 domain-containing protein 2; COMPND 4 CHAIN: A; COMPND 5 ENGINEERED: YES; EXPDTA X-RAY DIFFRACTION REMARK 2 RESOLUTION. 1.39 ANGSTORMS DBREF 6MAA A 10 78 UNP Q7TQN3 WFKN2_MOUSE 104 172 SEQRES 1 A 34 GLY LEU VAL PRO ARG GLY SER HIS MET ALA THR CYS ASP SEQRES 2 A 34 HIS PHE MET CYS LEU GLN GLN GLY SER GLU CYS ASP ILE SEQRES 3 A 34 TRP ASP GLY GLN PRO VAL CYS LYS ATOM 1 N GLY A 1 -28.946 17.899 -27.094 1.00 23.53 ATOM 2 CA GLY A 1 -29.298 17.159 -25.897 1.00 20.25 ATOM 3 C GLY A 1 -29.624 15.698 -26.154 1.00 14.64 ATOM 4 O GLY A 1 -30.189 15.025 -25.296 1.00 16.11 ATOM 5 N LEU A 2 -29.265 15.204 -27.338 1.00 13.51 ATOM 6 CA LEU A 2 -29.419 13.791 -27.658 1.00 11.62 ATOM 7 C LEU A 2 -28.330 13.001 -26.944 1.00 11.25 ATOM 8 O LEU A 2 -27.140 13.299 -27.096 1.00 12.13 ATOM 9 CB LEU A 2 -29.302 13.593 -29.168 1.00 13.47 ATOM 10 CG LEU A 2 -29.564 12.162 -29.636 1.00 13.02 ATOM 11 CD1 LEU A 2 -31.049 11.841 -29.583 1.00 14.62 ATOM 12 CD2 LEU A 2 -28.995 11.922 -31.026 1.00 16.28 ATOM 13 N VAL A 3 -28.728 12.003 -26.159 1.00 9.42 ATOM 14 CA VAL A 3 -27.771 11.184 -25.415 1.00 9.98 ATOM 15 C VAL A 3 -28.157 9.721 -25.545 1.00 8.79 ATOM 16 O VAL A 3 -29.299 9.392 -25.900 1.00 9.07 ATOM 17 CB VAL A 3 -27.698 11.585 -23.919 1.00 10.83 ATOM 18 CG1 VAL A 3 -27.218 13.018 -23.761 1.00 12.62 ATOM 19 CG2 VAL A 3 -29.025 11.353 -23.215 1.00 12.43 ATOM 20 N PRO A 4 -27.230 8.809 -25.250 1.00 8.57 ATOM 21 CA PRO A 4 -27.610 7.393 -25.166 1.00 8.73 ATOM 22 C PRO A 4 -28.555 7.188 -23.989 1.00 8.18 ATOM 23 O PRO A 4 -28.299 7.667 -22.881 1.00 10.52 ATOM 24 CB PRO A 4 -26.275 6.669 -24.939 1.00 8.66 ATOM 25 CG PRO A 4 -25.203 7.693 -25.137 1.00 10.17 ATOM 26 CD PRO A 4 -25.815 9.025 -24.901 1.00 9.49 ATOM 27 N ARG A 5 -29.661 6.496 -24.236 1.00 9.96 ATOM 28 CA ARG A 5 -30.586 6.183 -23.158 1.00 10.96 ATOM 29 C ARG A 5 -29.911 5.246 -22.155 1.00 14.33 ATOM 30 O ARG A 5 -29.083 4.403 -22.515 1.00 14.62 ATOM 31 CB ARG A 5 -31.850 5.533 -23.730 1.00 12.72 ATOM 32 CG ARG A 5 -32.956 5.276 -22.703 1.00 14.38 ATOM 33 CD ARG A 5 -34.270 4.856 -23.373 1.00 15.49 ATOM 34 NE ARG A 5 -34.928 5.955 -24.076 1.00 18.18 ATOM 35 CZ ARG A 5 -35.717 6.855 -23.495 1.00 18.45 ATOM 36 NH1 ARG A 5 -35.942 6.804 -22.187 1.00 20.12 ATOM 37 NH2 ARG A 5 -36.277 7.814 -24.222 1.00 19.82 ATOM 38 N GLY A 6 -30.250 5.411 -20.881 1.00 14.92 ATOM 39 CA GLY A 6 -29.625 4.559 -19.876 1.00 15.62 ATOM 40 C GLY A 6 -28.131 4.774 -19.740 1.00 14.79 ATOM 41 O GLY A 6 -27.370 3.806 -19.592 1.00 15.74 ATOM 42 N SER A 7 -27.694 6.025 -19.783 1.00 13.47 ATOM 43 CA SER A 7 -26.313 6.388 -19.529 1.00 12.02 ATOM 44 C SER A 7 -26.312 7.638 -18.669 1.00 10.66 ATOM 45 O SER A 7 -27.311 8.353 -18.577 1.00 12.42 ATOM 46 CB SER A 7 -25.531 6.651 -20.827 1.00 10.78 ATOM 47 OG SER A 7 -25.980 7.831 -21.483 1.00 10.86 ATOM 48 N HIS A 8 -25.176 7.890 -18.028 1.00 9.53 ATOM 49 CA HIS A 8 -25.006 9.103 -17.247 1.00 9.94 ATOM 50 C HIS A 8 -23.516 9.354 -17.106 1.00 7.92 ATOM 51 O HIS A 8 -22.704 8.429 -17.195 1.00 8.66 ATOM 52 CB HIS A 8 -25.670 8.975 -15.870 1.00 12.18 ATOM 53 CG HIS A 8 -25.927 10.284 -15.193 1.00 14.84 ATOM 54 ND1 HIS A 8 -24.968 10.939 -14.450 1.00 15.54 ATOM 55 CD2 HIS A 8 -27.041 11.054 -15.134 1.00 15.87 ATOM 56 CE1 HIS A 8 -25.479 12.055 -13.961 1.00 17.04 ATOM 57 NE2 HIS A 8 -26.736 12.148 -14.359 1.00 18.39 ATOM 58 N MET A 9 -23.162 10.615 -16.888 1.00 9.35 ATOM 59 CA MET A 9 -21.780 10.929 -16.561 1.00 9.77 ATOM 60 C MET A 9 -21.433 10.403 -15.172 1.00 8.47 ATOM 61 O MET A 9 -22.297 10.253 -14.301 1.00 9.46 ATOM 62 CB MET A 9 -21.558 12.436 -16.584 1.00 13.07 ATOM 63 CG MET A 9 -21.694 13.028 -17.986 1.00 17.45 ATOM 64 SD MET A 9 -21.271 14.772 -18.086 1.00 26.74 ATOM 65 CE MET A 9 -22.475 15.461 -16.961 1.00 29.10 ATOM 66 N ALA A 10 -20.149 10.118 -14.972 1.00 8.72 ATOM 67 CA ALA A 10 -19.668 9.694 -13.665 1.00 8.24 ATOM 68 C ALA A 10 -19.474 10.898 -12.751 1.00 9.14 ATOM 69 O ALA A 10 -19.202 12.010 -13.212 1.00 10.19 ATOM 70 CB ALA A 10 -18.348 8.938 -13.813 1.00 9.70 ATOM 71 N THR A 11 -19.609 10.667 -11.439 1.00 9.22 ATOM 72 CA THR A 11 -19.486 11.727 -10.443 1.00 8.96 ATOM 73 C THR A 11 -18.705 11.234 -9.226 1.00 9.40 ATOM 74 O THR A 11 -18.603 10.034 -8.966 1.00 9.26 ATOM 75 CB THR A 11 -20.854 12.252 -9.972 1.00 11.12 ATOM 76 OG1 THR A 11 -21.514 11.238 -9.204 1.00 13.44 ATOM 77 CG2 THR A 11 -21.739 12.665 -11.149 1.00 13.37 ATOM 78 N CYS A 12 -18.182 12.191 -8.459 1.00 9.35 ATOM 79 CA CYS A 12 -17.321 11.928 -7.307 1.00 10.24 ATOM 80 C CYS A 12 -18.064 11.800 -5.975 1.00 9.92 ATOM 81 O CYS A 12 -17.416 11.517 -4.962 1.00 10.00 ATOM 82 CB CYS A 12 -16.266 13.035 -7.178 1.00 10.85 ATOM 83 SG CYS A 12 -14.810 12.810 -8.230 1.00 12.54 ATOM 84 N ASP A 13 -19.392 11.972 -5.953 1.00 10.06 ATOM 85 CA ASP A 13 -20.137 12.085 -4.695 1.00 10.34 ATOM 86 C ASP A 13 -19.805 10.969 -3.710 1.00 10.51 ATOM 87 O ASP A 13 -19.588 11.222 -2.520 1.00 12.67 ATOM 88 CB ASP A 13 -21.643 12.085 -4.971 1.00 13.43 ATOM 89 CG ASP A 13 -22.077 13.231 -5.855 1.00 15.08 ATOM 90 OD1 ASP A 13 -21.733 13.210 -7.050 1.00 15.33 ATOM 91 OD2 ASP A 13 -22.759 14.149 -5.357 1.00 19.77 ATOM 92 N HIS A 14 -19.807 9.720 -4.176 1.00 8.89 ATOM 93 CA HIS A 14 -19.635 8.574 -3.297 1.00 9.41 ATOM 94 C HIS A 14 -18.211 8.037 -3.279 1.00 8.37 ATOM 95 O HIS A 14 -17.999 6.869 -2.925 1.00 8.83 ATOM 96 CB HIS A 14 -20.653 7.485 -3.625 1.00 9.34 ATOM 97 CG HIS A 14 -22.048 7.849 -3.248 1.00 9.89 ATOM 98 ND1 HIS A 14 -22.428 8.055 -1.938 1.00 13.78 ATOM 99 CD2 HIS A 14 -23.158 8.045 -3.994 1.00 12.85 ATOM 100 CE1 HIS A 14 -23.711 8.359 -1.896 1.00 14.55 ATOM 101 NE2 HIS A 14 -24.181 8.356 -3.131 1.00 14.38 ATOM 102 N PHE A 15 -17.231 8.878 -3.597 1.00 8.99 ATOM 103 CA PHE A 15 -15.826 8.527 -3.502 1.00 8.98 ATOM 104 C PHE A 15 -15.127 9.485 -2.551 1.00 9.67 ATOM 105 O PHE A 15 -15.550 10.631 -2.382 1.00 11.19 ATOM 106 CB PHE A 15 -15.151 8.578 -4.878 1.00 9.49 ATOM 107 CG PHE A 15 -15.659 7.534 -5.823 1.00 8.84 ATOM 108 CD1 PHE A 15 -15.099 6.268 -5.844 1.00 10.11 ATOM 109 CD2 PHE A 15 -16.713 7.808 -6.674 1.00 10.32 ATOM 110 CE1 PHE A 15 -15.579 5.292 -6.711 1.00 9.87 ATOM 111 CE2 PHE A 15 -17.199 6.841 -7.533 1.00 10.73 ATOM 112 CZ PHE A 15 -16.629 5.585 -7.559 1.00 9.78 ATOM 113 N MET A 16 -14.058 8.995 -1.928 1.00 9.93 ATOM 114 CA MET A 16 -13.189 9.819 -1.105 1.00 10.88 ATOM 115 C MET A 16 -11.746 9.473 -1.423 1.00 9.76 ATOM 116 O MET A 16 -11.423 8.337 -1.773 1.00 11.44 ATOM 117 CB MET A 16 -13.462 9.579 0.390 1.00 17.60 ATOM 118 CG MET A 16 -12.798 10.582 1.328 1.00 25.37 ATOM 119 SD MET A 16 -13.220 10.262 3.052 1.00 36.96 ATOM 120 CE MET A 16 -12.313 8.747 3.335 1.00 25.40 ATOM 121 N CYS A 17 -10.876 10.462 -1.294 1.00 12.13 ATOM 122 CA CYS A 17 -9.448 10.284 -1.505 1.00 12.54 ATOM 123 C CYS A 17 -8.752 10.370 -0.155 1.00 13.36 ATOM 124 O CYS A 17 -8.824 11.404 0.517 1.00 15.94 ATOM 125 CB CYS A 17 -8.930 11.351 -2.463 1.00 12.33 ATOM 126 SG CYS A 17 -9.546 11.127 -4.147 1.00 13.71 ATOM 127 N LEU A 18 -8.083 9.283 0.239 1.00 13.52 ATOM 128 CA LEU A 18 -7.484 9.226 1.572 1.00 15.78 ATOM 129 C LEU A 18 -6.299 10.170 1.721 1.00 15.89 ATOM 130 O LEU A 18 -6.007 10.614 2.838 1.00 17.77 ATOM 131 CB LEU A 18 -7.056 7.797 1.911 1.00 17.50 ATOM 132 CG LEU A 18 -8.158 6.753 2.110 1.00 19.82 ATOM 133 CD1 LEU A 18 -7.550 5.403 2.434 1.00 21.33 ATOM 134 CD2 LEU A 18 -9.097 7.184 3.216 1.00 23.10 ATOM 135 N GLN A 19 -5.601 10.480 0.630 1.00 14.86 ATOM 136 CA GLN A 19 -4.396 11.295 0.718 1.00 15.08 ATOM 137 C GLN A 19 -4.725 12.700 1.197 1.00 14.16 ATOM 138 O GLN A 19 -5.575 13.390 0.628 1.00 14.69 ATOM 139 CB GLN A 19 -3.711 11.365 -0.645 1.00 14.83 ATOM 140 CG GLN A 19 -2.611 12.411 -0.740 1.00 15.53 ATOM 141 CD GLN A 19 -1.433 12.112 0.171 1.00 16.01 ATOM 142 OE1 GLN A 19 -0.869 11.019 0.131 1.00 18.92 ATOM 143 NE2 GLN A 19 -1.051 13.088 0.992 1.00 15.23 ATOM 144 N GLN A 20 -4.035 13.120 2.252 1.00 13.95 ATOM 145 CA GLN A 20 -4.137 14.485 2.742 1.00 13.64 ATOM 146 C GLN A 20 -3.865 15.475 1.614 1.00 13.32 ATOM 147 O GLN A 20 -2.888 15.337 0.874 1.00 13.28 ATOM 148 CB GLN A 20 -3.095 14.648 3.843 1.00 14.16 ATOM 149 CG GLN A 20 -2.991 16.013 4.436 1.00 12.83 ATOM 150 CD GLN A 20 -1.990 16.029 5.555 1.00 12.94 ATOM 151 OE1 GLN A 20 -1.364 15.010 5.845 1.00 14.86 ATOM 152 NE2 GLN A 20 -1.820 17.181 6.189 1.00 13.22 ATOM 153 N GLY A 21 -4.753 16.463 1.473 1.00 13.36 ATOM 154 CA GLY A 21 -4.625 17.491 0.457 1.00 13.84 ATOM 155 C GLY A 21 -5.166 17.131 -0.909 1.00 13.42 ATOM 156 O GLY A 21 -5.057 17.945 -1.835 1.00 13.59 ATOM 157 N SER A 22 -5.752 15.953 -1.068 1.00 13.98 ATOM 158 CA SER A 22 -6.234 15.495 -2.359 1.00 14.85 ATOM 159 C SER A 22 -7.755 15.558 -2.400 1.00 15.35 ATOM 160 O SER A 22 -8.428 15.649 -1.370 1.00 17.93 ATOM 161 CB SER A 22 -5.764 14.064 -2.613 1.00 16.99 ATOM 162 OG SER A 22 -6.490 13.151 -1.821 1.00 19.98 ATOM 163 N GLU A 23 -8.294 15.517 -3.615 1.00 14.33 ATOM 164 CA GLU A 23 -9.735 15.441 -3.788 1.00 15.02 ATOM 165 C GLU A 23 -10.039 14.632 -5.039 1.00 12.67 ATOM 166 O GLU A 23 -9.193 14.463 -5.920 1.00 14.00 ATOM 167 CB GLU A 23 -10.381 16.830 -3.861 1.00 20.09 ATOM 168 CG GLU A 23 -10.101 17.581 -5.152 1.00 24.54 ATOM 169 CD GLU A 23 -10.811 18.923 -5.218 1.00 29.43 ATOM 170 OE1 GLU A 23 -10.722 19.588 -6.273 1.00 33.81 ATOM 171 OE2 GLU A 23 -11.454 19.314 -4.220 1.00 29.82 ATOM 172 N CYS A 24 -11.259 14.116 -5.088 1.00 12.25 ATOM 173 CA CYS A 24 -11.709 13.338 -6.231 1.00 11.89 ATOM 174 C CYS A 24 -12.009 14.260 -7.406 1.00 11.76 ATOM 175 O CYS A 24 -12.532 15.366 -7.233 1.00 13.71 ATOM 176 CB CYS A 24 -12.956 12.541 -5.843 1.00 11.34 ATOM 177 SG CYS A 24 -13.676 11.509 -7.142 1.00 12.42 ATOM 178 N ASP A 25 -11.659 13.794 -8.602 1.00 10.58 ATOM 179 CA ASP A 25 -12.002 14.431 -9.866 1.00 11.08 ATOM 180 C ASP A 25 -12.423 13.321 -10.821 1.00 11.26 ATOM 181 O ASP A 25 -12.120 12.147 -10.595 1.00 14.05 ATOM 182 CB ASP A 25 -10.784 15.197 -10.430 1.00 13.57 ATOM 183 CG ASP A 25 -11.157 16.282 -11.447 1.00 15.79 ATOM 184 OD1 ASP A 25 -12.344 16.448 -11.800 1.00 17.77 ATOM 185 OD2 ASP A 25 -10.231 16.981 -11.899 1.00 18.52 ATOM 186 N ILE A 26 -13.146 13.685 -11.877 1.00 11.00 ATOM 187 CA ILE A 26 -13.567 12.733 -12.901 1.00 10.46 ATOM 188 C ILE A 26 -12.723 12.980 -14.144 1.00 11.79 ATOM 189 O ILE A 26 -12.799 14.055 -14.752 1.00 14.19 ATOM 190 CB ILE A 26 -15.070 12.839 -13.209 1.00 10.76 ATOM 191 CG1 ILE A 26 -15.909 12.498 -11.971 1.00 11.94 ATOM 192 CG2 ILE A 26 -15.447 11.936 -14.388 1.00 12.20 ATOM 193 CD1 ILE A 26 -15.759 11.074 -11.500 1.00 12.06 ATOM 194 N TRP A 27 -11.925 11.983 -14.526 1.00 10.84 ATOM 195 CA TRP A 27 -11.113 12.046 -15.735 1.00 11.34 ATOM 196 C TRP A 27 -11.421 10.842 -16.609 1.00 11.80 ATOM 197 O TRP A 27 -11.370 9.702 -16.139 1.00 11.91 ATOM 198 CB TRP A 27 -9.623 12.080 -15.384 1.00 14.99 ATOM 199 CG TRP A 27 -9.124 13.468 -15.173 1.00 19.69 ATOM 200 CD1 TRP A 27 -9.292 14.239 -14.058 1.00 22.54 ATOM 201 CD2 TRP A 27 -8.384 14.266 -16.107 1.00 19.08 ATOM 202 NE1 TRP A 27 -8.699 15.465 -14.240 1.00 23.38 ATOM 203 CE2 TRP A 27 -8.132 15.505 -15.488 1.00 23.47 ATOM 204 CE3 TRP A 27 -7.903 14.048 -17.401 1.00 20.38 ATOM 205 CZ2 TRP A 27 -7.425 16.529 -16.124 1.00 24.20 ATOM 206 CZ3 TRP A 27 -7.202 15.065 -18.030 1.00 23.85 ATOM 207 CH2 TRP A 27 -6.970 16.287 -17.390 1.00 24.90 ATOM 208 N ASP A 28 -11.734 11.101 -17.880 1.00 11.38 ATOM 209 CA ASP A 28 -12.115 10.047 -18.821 1.00 11.24 ATOM 210 C ASP A 28 -13.193 9.138 -18.234 1.00 10.85 ATOM 211 O ASP A 28 -13.156 7.915 -18.374 1.00 12.28 ATOM 212 CB ASP A 28 -10.902 9.254 -19.309 1.00 14.15 ATOM 213 CG ASP A 28 -9.934 10.111 -20.085 1.00 20.05 ATOM 214 OD1 ASP A 28 -10.383 11.129 -20.642 1.00 20.86 ATOM 215 OD2 ASP A 28 -8.735 9.767 -20.145 1.00 25.27 ATOM 216 N GLY A 29 -14.157 9.748 -17.550 1.00 10.90 ATOM 217 CA GLY A 29 -15.280 9.007 -17.031 1.00 10.84 ATOM 218 C GLY A 29 -15.009 8.159 -15.811 1.00 9.75 ATOM 219 O GLY A 29 -15.848 7.312 -15.483 1.00 11.71 ATOM 220 N GLN A 30 -13.881 8.348 -15.128 1.00 10.50 ATOM 221 CA GLN A 30 -13.560 7.573 -13.938 1.00 11.53 ATOM 222 C GLN A 30 -13.091 8.483 -12.819 1.00 10.96 ATOM 223 O GLN A 30 -12.410 9.488 -13.065 1.00 11.91 ATOM 224 CB GLN A 30 -12.452 6.546 -14.221 1.00 14.17 ATOM 225 CG GLN A 30 -12.769 5.581 -15.354 1.00 16.89 ATOM 226 CD GLN A 30 -11.721 4.498 -15.504 1.00 23.80 ATOM 227 OE1 GLN A 30 -11.863 3.403 -14.959 1.00 30.12 ATOM 228 NE2 GLN A 30 -10.659 4.798 -16.240 1.00 24.77 ATOM 229 N PRO A 31 -13.413 8.144 -11.567 1.00 10.23 ATOM 230 CA PRO A 31 -12.889 8.910 -10.430 1.00 11.10 ATOM 231 C PRO A 31 -11.393 8.691 -10.263 1.00 11.23 ATOM 232 O PRO A 31 -10.892 7.569 -10.376 1.00 13.31 ATOM 233 CB PRO A 31 -13.662 8.341 -9.234 1.00 11.93 ATOM 234 CG PRO A 31 -13.982 6.951 -9.634 1.00 13.87 ATOM 235 CD PRO A 31 -14.263 7.022 -11.125 1.00 12.36 ATOM 236 N VAL A 32 -10.683 9.790 -9.996 1.00 10.78 ATOM 237 CA VAL A 32 -9.255 9.785 -9.708 1.00 12.09 ATOM 238 C VAL A 32 -9.016 10.768 -8.568 1.00 12.19 ATOM 239 O VAL A 32 -9.865 11.604 -8.256 1.00 13.74 ATOM 240 CB VAL A 32 -8.411 10.182 -10.947 1.00 14.16 ATOM 241 CG1 VAL A 32 -8.615 9.193 -12.098 1.00 16.26 ATOM 242 CG2 VAL A 32 -8.751 11.599 -11.388 1.00 16.77 ATOM 243 N CYS A 33 -7.847 10.667 -7.939 1.00 13.24 ATOM 244 CA CYS A 33 -7.459 11.572 -6.862 1.00 13.42 ATOM 245 C CYS A 33 -6.376 12.527 -7.344 1.00 14.28 ATOM 246 O CYS A 33 -5.394 12.100 -7.962 1.00 19.01 ATOM 247 CB CYS A 33 -6.968 10.791 -5.643 1.00 15.54 ATOM 248 SG CYS A 33 -8.252 9.773 -4.913 1.00 16.34 ATOM 249 N LYS A 34 -6.568 13.817 -7.069 1.00 14.50 ATOM 250 CA LYS A 34 -5.639 14.862 -7.482 1.00 16.19 ATOM 251 C LYS A 34 -5.437 15.841 -6.334 1.00 15.04 ATOM 252 O LYS A 34 -6.320 16.029 -5.499 1.00 15.95 ATOM 253 CB LYS A 34 -6.179 15.629 -8.701 1.00 19.94 ATOM 254 CG LYS A 34 -6.505 14.753 -9.891 1.00 24.65 ATOM 255 CD LYS A 34 -5.243 14.144 -10.472 1.00 28.76 ATOM 256 CE LYS A 34 -5.487 13.599 -11.869 1.00 32.10 ATOM 257 NZ LYS A 34 -5.959 14.667 -12.790 1.00 33.15 ATOM 258 N NO3 A 101 -21.238 13.662 -21.472 1.00 27.02 ATOM 259 O1 NO3 A 101 -20.829 12.469 -21.439 1.00 22.19 ATOM 260 O2 NO3 A 101 -22.479 13.904 -21.444 1.00 25.50 ATOM 261 O3 NO3 A 101 -20.402 14.613 -21.530 1.00 34.35 TER