Xu G, Evans J S
Laboratory for Chemical Physics, New York University, NY 10010, USA.
Biopolymers. 1999 Apr;49(4):303-12. doi: 10.1002/(SICI)1097-0282(19990405)49:4<303::AID-BIP5>3.0.CO;2-4.
We report solution-state pulsed field gradient nmr studies of a native sequence-derived 23-residue peptidomimetic, N alpha-acetyl-QPGVGGRQPGMGGQPGVGGRQPG-C alpha-amid, that incorporates the prevalent GVGGR and GMGGQ repeats found in the sea urchin embryo intracrystalline spicule matrix protein, SM50 (Strongylocentrotus purpuratus). These repeats are sequence homologues of elastin protein repeats (VPGVG, VGGVG, and APGVGV) and spider dragline silk protein repeats (GPGG, GQGG, and QPGYG). Using rotating frame nuclear Overhauser effect (ROE) connectivities, CH alpha proton conformational shifts, 3JNH-CH alpha coupling constants, amide temperature shift coefficients, and pulsed field gradient ROE spectroscopy solvent exchange measurements, we find that the 23-mer peptidomimetic possesses a multiple beta-turn structure in aqueous solution, in equilibria with an extended or coil structure (60% beta-turn: 40% random coil). The GVGGR sequence adopts a double beta-turn conformation that is stabilized by two hydrogen bonds (R7-->V4, R20-->V17; G6-->G3, G19-->G16). The GMGGQ region adopts a single beta-turn conformation that is stabilized by a hydrogen bond involving residues Q14 and M11. Repeating beta-turn structures, or beta-spirals, may play an important role with regard to matrix assembly, protein stability, molecular elasticity, and/or protein-crystal recognition within the spicule mineralized matrix.
我们报告了对一种天然序列衍生的23个残基的拟肽Nα-乙酰基-QPGVGGRQPGMGGQPGVGGRQPG-Cα-酰胺的溶液态脉冲场梯度核磁共振研究，该拟肽包含在海胆胚胎晶体内针状基质蛋白SM50（紫海胆）中发现的常见GVGGR和GMGGQ重复序列。这些重复序列是弹性蛋白重复序列（VPGVG、VGGVG和APGVGV）以及蜘蛛拖丝蛋白重复序列（GPGG、GQGG和QPGYG）的序列同源物。利用旋转坐标系核Overhauser效应（ROE）连接性、CHα质子构象位移、3JNH-CHα耦合常数、酰胺温度位移系数以及脉冲场梯度ROE光谱溶剂交换测量，我们发现该23聚体拟肽在水溶液中具有多重β-转角结构，与伸展或卷曲结构处于平衡状态（60%β-转角：40%无规卷曲）。GVGGR序列采用由两个氢键（R7→V4，R20→V17；G6→G3，G19→G16）稳定的双β-转角构象。GMGGQ区域采用由涉及残基Q14和M11的氢键稳定的单β-转角构象。重复的β-转角结构，即β-螺旋，可能在针状矿化基质内的基质组装、蛋白质稳定性、分子弹性和/或蛋白质-晶体识别方面发挥重要作用。
