Malashkevich V N, Kammerer R A, Efimov V P, Schulthess T, Engel J
Department of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Science. 1996 Nov 1;274(5288):761-5. doi: 10.1126/science.274.5288.761.
Oligomerization by the formation of alpha-helical bundles is common in many proteins. The crystal structure of a parallel pentameric coiled coil, constituting the oligomerization domain in the cartilage oligomeric matrix protein (COMP), was determined at 2.05 angstroms resolution. The same structure probably occurs in two other extracellular matrix proteins, thrombospondins 3 and 4. Complementary hydrophobic interactions and conserved disulfide bridges between the alpha helices result in a thermostable structure with unusual properties. The long hydrophobic axial pore is filled with water molecules but can also accommodate small apolar groups. An "ion trap" is formed inside the pore by a ring of conserved glutamines, which binds chloride and probably other monatomic anions. The oligomerization domain of COMP has marked similarities with proposed models of the pentameric transmembrane ion channels in phospholamban and the acetylcholine receptor.
通过形成α-螺旋束进行寡聚化在许多蛋白质中很常见。软骨寡聚基质蛋白（COMP）中构成寡聚化结构域的平行五聚体卷曲螺旋的晶体结构在2.05埃分辨率下被确定。相同的结构可能也存在于另外两种细胞外基质蛋白，血小板反应蛋白3和4中。α-螺旋之间互补的疏水相互作用和保守的二硫键导致了一种具有异常性质的热稳定结构。长的疏水轴向孔充满了水分子，但也能容纳小的非极性基团。孔内由一圈保守的谷氨酰胺形成一个“离子阱”，它结合氯离子以及可能的其他单原子阴离子。COMP的寡聚化结构域与肌浆网钙转运ATP酶和乙酰胆碱受体中提出的五聚体跨膜离子通道模型有显著相似性。
