轉彎序列對b-摺板結構的影響
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2006
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我們引用Gellman 在1998年設計出的一個可單獨存在且具有良好水溶性的b-摺板結構作為模板，將第六個位置的DP突變成D時，稱之為P6D，此時N端髮夾結構的轉彎序列由原本的DP-G ( Type II’ turn) 變成由五個氨基酸所組成的T-S-D-G-K ( Type I + b bulge )，造成N端髮夾結構氨基酸相對位置的改變；而繼續在第14個位置做相同突變時，稱之為P6DP14D，C端髮夾結構並無相對位置上的改變。本研究將Gellman胜肽N端髮夾的序列S-DP-G-K置換成P6DP14D在C端髮夾所形成的轉彎序列V-D-G-O，稱之為M-T20mer，探討其將會形成何種轉彎序列並探討其與P6D的差異何在，並將此胜肽C端髮夾位置做相同的置換，稱之M-TP14D，可完整探討轉彎序列和疏水性作用力對蛋白質摺疊的影響。我們主要利用核磁共振光譜、圓二色光譜，和結構的計算等方法進行研究，結果得到擁有V-D-G-O序列的胜肽在最終結構獲得較高的穩定性，但在摺疊的過程中因必須靠疏水性作用力 (此疏水性基團包含第三個b-長帶) 的幫助而較慢形成。
We used the three-stranded b-sheet 20mer peptide, VFITSDPGKT YTEVDPGOKILQ, designed by Schenck and Gellman (1998), as the model peptide to exploit conformational stability of the structure between the effects of the turn sequence and the hydrophobic collapse using various mutation of the peptide. M-T20mer, one of the corresponding mutant peptides, wherein the TSDPGK turn sequence in the N-terminal hairpin was replaced by TVDGO, was synthesized. The turn structure was shown to altered with this change. We further mutated the DP to D in C-terminal hairpin of M-T20mer, denoted as M-TP14D, to compare the difference between our earlier studies on P6D and P6DP14D18. NMR spectra and simulated annealing methods were cored to solve the structure of these peptides. CD spectra were cored to show the different secondary structural features of these peptides. We concluded that the M-T20mer peptide has a 2:2 type I’ turn VDGO. The 20mer peptide with the V-D-G-O turn sequence in N-terminal hairpin was stabilized by hydrophobic collapse involving the third strand, whereas the 20mer peptide with T-S-D-G-K turn sequence (P6D mutation) was stabilized by the N-terminal turn.
We used the three-stranded b-sheet 20mer peptide, VFITSDPGKT YTEVDPGOKILQ, designed by Schenck and Gellman (1998), as the model peptide to exploit conformational stability of the structure between the effects of the turn sequence and the hydrophobic collapse using various mutation of the peptide. M-T20mer, one of the corresponding mutant peptides, wherein the TSDPGK turn sequence in the N-terminal hairpin was replaced by TVDGO, was synthesized. The turn structure was shown to altered with this change. We further mutated the DP to D in C-terminal hairpin of M-T20mer, denoted as M-TP14D, to compare the difference between our earlier studies on P6D and P6DP14D18. NMR spectra and simulated annealing methods were cored to solve the structure of these peptides. CD spectra were cored to show the different secondary structural features of these peptides. We concluded that the M-T20mer peptide has a 2:2 type I’ turn VDGO. The 20mer peptide with the V-D-G-O turn sequence in N-terminal hairpin was stabilized by hydrophobic collapse involving the third strand, whereas the 20mer peptide with T-S-D-G-K turn sequence (P6D mutation) was stabilized by the N-terminal turn.
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b-摺板, 轉彎序列, b-hairpin, turn sequence