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HBV DNA多聚酶包含4个小的高度保守的结构域,分别为A、B、C、D区,YMDD基序位于C区,YMDD是指酪氨酸(Y)-蛋氨酸(M)-天门冬氨酸(D)-天门冬氨酸(D)。YMDD基序是DNA多聚酶的活性部位,拉米夫定结合于此区,干扰HBV的复制。长期应用(一般在6个月以上)拉米夫定后可出现YMDD变异,YMDD变异共分2型:Ⅰ型YMDD变异为HBV DNA多聚酶C区第522第密码子蛋氨酸(M)被缬氨酸(V)取代(M522V)成为YVDD。此型变异常同时伴有HBV DNA多聚酶B区第528个密码子亮氨酸(L)被蛋氨酸取代(L528M)。Ⅱ型YMDD变异为HBV DNA多聚酶C区第522个密码子被异亮氨酸(I)
The HBV DNA polymerase contains four small, highly conserved domains, A, B, C and D, the YMDD motif is located in region C, and YMDD refers to tyrosine (Y) -methionine (M) Acid (D) - Aspartic acid (D). The YMDD motif is the active site of DNA polymerase, and lamivudine binds to this region and interferes with HBV replication. Long-term use (usually more than 6 months) after lamivudine YMDD mutation can occur, YMDD mutation is divided into two types: Ⅰ type YMDD mutation HBV DNA polymerase C region codon 54 of codon methionine (M) is valine (V) Substitution (M522V) becomes YVDD. This type of aberration is accompanied by the simultaneous replacement of the 528th codon Leu (L) in the HBV DNA polymerase B region by methionine (L528M). Type II YMDD mutation is HBV DNA polymerase C region 522th codon isoleucine (I)