原子分辨率结构CTX-M beta-lactamases:扩展频谱活动增加流动性和减少稳定。
文章的细节
-
引用
-
陈Y,戴J, Sirot J, Shoichet B,阀盖R
原子分辨率结构CTX-M beta-lactamases:扩展频谱活动增加流动性和减少稳定。
J杂志。2005年4月29日,348 (2):349 - 62。
- PubMed ID
-
15811373 (在PubMed]
- 文摘
-
扩展频谱beta-lactamases (ESBLs)赋予细菌对第三代头孢菌素如头孢噻肟和头孢他啶,医院死亡率增加。而这些抗生素几乎不受经典beta-lactamases,如TEM-1 ESBLs有1 - 4订单大的活动。这个活动被广泛研究的起源TEM和SHV-type ESBLs,但收到的关注更少CTX-M beta-lactamases,一个新兴的家族,现在占主导地位的ESBL在几个地区。了解CTX-M beta-lactamases实现他们非凡的活动,生物物理和结构研究。使用可逆,两国热变性,发现随着这些酶的发展更广泛的底物范围,他们牺牲稳定。因此,突变体酶CTX-M-16比pseudo-wild-type 8倍更积极的对头孢他啶CTX-M-14但是是1.9千卡/摩尔更不稳定。这是符合“stability-activity权衡”,类似于在其他抵抗酶的进化。探讨酶活性和稳定性的结构基础,四个CTX-M酶的结构是由x射线晶体学。CTX-M-14的结构、CTX-M-27 CTX-M-9和CTX-M-16决心1.10埃,1.20埃,分别为0.98埃和1.74埃分辨率。相似的酶活性位点的窄谱TEM-1 SHV-1,而不是扩大网站的典型ESBL TEM-52和tem - 64等突变体。 Instead, point substitutions leading to specific interactions may be responsible for the improved activity against ceftazidime and cefotaxime, consistent with observations first made for the related Toho-1 enzyme. The broadened substrate range of CTX-M-16 may result from coupled defects in the enzyme's B3 strand, which lines the active site. Substitutions Val231-->Ala and Asp240-->Gly, which convert CTX-M-14 into CTX-M-16, occur at either end of this strand. These defects appear to increase the mobility of B3 based on anisotropic B-factor analyses at ultrahigh resolution, consistent with stability loss and activity gain. The unusually high resolution of these structures that makes such analyses possible also makes them good templates for inhibitor discovery.