Abstract：
Low density lipoprotein receptor domains (LDLrs) represent a large cell surface receptor superfamily of consensus length 39 residues. Alignment of 194 sequences indicated highly conserved Cys and Asp/Glu residues, and a consensus secondary structure with three beta-strands was predicted. Sequence threading against known protein folds indicated consistency with small beta-sheet proteins. Complement factor I contains two LDLrs, and the second of these was successfully expressed using a bacterial pGEX system. FT-IR spectroscopy on this indicated a small amount of beta-sheet together with turns and loops. LDLr is proposed to have a beta-sheet structure in which the five biologically important Asp/Glu residues are located on an exposed loop.
摘要：
低密度脂蛋白受体结构域(LDLrs)代表共有长度为39个残基的大细胞表面受体超家族。194个序列的比对显示高度保守的Cys和Asp/Glu残基，并预测了具有三个β链的共有二级结构。针对已知蛋白质折叠的序列穿线表明与小β折叠蛋白的一致性。补体因子I包含两个LDLr，第二个是使用细菌pGEX系统成功表达的。对此的FT-IR光谱表明少量的β-折叠以及匝和环。LDLr被认为具有β-折叠结构,其中5个生物学上重要的Asp/Glu残基位于暴露的环上。
