Tertiary structure of human λ6 light chains
Tertiary structure of human λ6 light chains
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DOI：
10.3109/13506129909007322
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发表时间：
1999-09-01
期刊：
影响因子：
--
通讯作者：
Schiffer, M
中科院分区：
文献类型：
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作者：
Pokkuluri, PR;Solomon, A;Schiffer, M
淀粉样变性是一种以组织中单克隆性轻链病理性沉积为特征的疾病过程。到目前为止，关于导致这种轻链淀粉样变性的分子特征的信息有限。虽然人类主要的V-kappa和V-lambda基因家族的蛋白产物已经在AL沉积物中被发现，但有一个特殊的亚群-lambda 6-被发现与这种疾病优先相关。值得注意的是，lambda 6蛋白的可变区(V(Lambda)6)具有独特的一级结构特征，包括在第三框架区(FR3)存在两个额外的氨基酸残基，这将该亚群的成员与其他类型的轻链区分开来。然而，这些变化的结构后果尚未阐明。为了确定lambda 6蛋白是否具有独特的三级结构特征，与其他V-lambda亚基的轻链相比，我们获得了两个重组V(Lambda)6分子晶体的X射线衍射数据。这些成分是从细菌表达系统中分离出来的，从一名确诊为AL淀粉样变性的患者(WIL)和另一名患有多发性骨髓瘤和管型管型肾病的患者(JTO)的骨髓浆细胞中克隆出lambda 6相关的cDNA，但没有明显的纤维沉积。X射线结晶学分析表明，位于68至69位之间(而不是先前推测的66至67位之间)的两个残基插入延长了现有的环区，有效地增加了第一互补决定区(CDR1)附近的表面积。此外，还注意到了在lambda 6分子中常见的Arg 25和Phe 2残基之间的不寻常的相互作用。然而，V(Lambda)6WIL和JTO的结构也不同，后者存在某些离子和疏水相互作用，我们认为这些相互作用增加了蛋白质的稳定性，从而防止了淀粉样蛋白的形成。
AL amyloidosis is a disease process characterized by the pathologic deposition of monoclonal light chains in tissue. To date, only limited information has been obtained on the molecular features that render such light chains amyloidogenic. Although protein products of the major human V-kappa and V-lambda gene families have been identified in AL deposits, one particular subgroup - lambda 6 - has been found to be preferentially associated with this disease. Notably, the variable region of lambda 6 proteins (V(lambda)6) has distinctive primary structural features including the presence in the third framework region (FR3) of two additional amino acid residues that distinguish members of this subgroup from other types of light chains. However, the structural consequences of these alterations have not been elucidated. To determine if lambda 6 proteins possess unique tertiary structural features, as compared to light chains of other V-lambda subgroups, we have obtained x-ray diffraction data on crystals prepared from two recombinant V(lambda)6 molecules. These components, isolated from a bacterial expression system, were generated from lambda 6-related cDNAs cloned from bone marrow-derived plasma cells from a patient (Wil) who had documented AL amyloidosis and another (Jto) with multiple myeloma and tubular cast nephropathy, but no evident fibrillar deposits. The xray crystallographic analyses revealed that the two-residue insertion located between positions 68 and 69 (not between 66 and 67 as previously surmised) extended an existing loop region that effectively increased the surface area adjacent to the first complementarity determining region (CDR1). Further, an unusual interaction between the Arg 25 and Phe 2 residues commonly found in lambda 6 molecules was noted. However, the structures of V(lambda)6 Wil and Jto also differed from each other, as evidenced by the presence in the latter of certain ionic and hydrophobic interactions that we posit increased protein stability and thus prevented amyloid formation.