3-DIMENSIONAL STRUCTURES OF AVIDIN AND THE AVIDIN-BIOTIN COMPLEX
3-DIMENSIONAL STRUCTURES OF AVIDIN AND THE AVIDIN-BIOTIN COMPLEX
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DOI：
10.1073/pnas.90.11.5076
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发表时间：
1993-06-01
影响因子：
11.1
通讯作者：
SUSSMAN, JL
中科院分区：
文献类型：
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作者：
LIVNAH, O;BAYER, EA;SUSSMAN, JL
蛋白糖蛋白亲和素的去糖基化形式及其与生物素的复合物的晶体结构已被确定为分别为2.6和3.0埃。结构揭示了对四聚体组装体的稳定和生物素的异常紧密结合至关重要的氨基酸残基。每个单体都是一个八链反平行β桶，与遗传上不同的细菌类似物链霉亲和素非常相似。如在链霉亲和素中，生物素的结合涉及极性和疏水相互作用的高度稳定的网络。然而，两者之间存在一些差异。亲和素结合位点中存在额外的疏水和亲水基团（链霉亲和素中缺少）可能是其较高亲和力常数的原因。两个氨基酸取代被认为是其相对于链霉亲和素对变性敏感的原因。出乎意料的是，通过差分傅立叶合成在去糖基化抗生物素蛋白单体中检测到残留的N-乙酰葡糖胺部分。
The crystal structures of a deglycosylated form of the egg-white glycoprotein avidin and of its complex with biotin have been determined to 2.6 and 3.0 angstrom, respectively. The structures reveal the amino acid residues critical for stabilization of the tetrameric assembly and for the exceptionally tight binding of biotin. Each monomer is an eight-stranded antiparallel beta-barrel, remarkably similar to that of the genetically distinct bacterial analog streptavidin. As in streptavidin, binding of biotin involves a highly stabilized network of polar and hydrophobic interactions. There are, however, some differences. The presence of additional hydrophobic and hydrophilic groups in the binding site of avidin (which are missing in streptavidin) may account for its higher affinity constant. Two amino acid substitutions are proposed to be responsible for its susceptibility to denaturation relative to streptavidin. Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer by difference Fourier synthesis.