Electric birefringence of recombinant spectrin segments 14, 14–15, 14–16, and 14–17 from Drosophila α-spectrin

摘要: Members of the spectrin protein family can be found in many different cells and organisms. In all cases studied, major functional role these proteins is believed to structural rather than enzymatic. All are highly elongated consist mainly homologous repeats that constitute rigid segments connected tandem. It commonly details function depend critically on flexibility links between segments. Here we report a work addressing this question by studying transient electric birefringence recombinant fragments consisting 14, 14–15, 14–16, 14–17, respectively, from Drosophila α-spectrin. Transient depends sharply both molecular length flexibility. We relaxation time segment 14 measured at 4°C, but scaled what expected 20°C, equals 16 ns (±15%) pH 7.5 ionic strength 6 mM. This consistent with single being rigid, 5 nm long having an axial ratio equal about two. Under same conditions, 14–16 14–17 show times 45, 39 164 (all ±20%), 20°C. When temperature increased 37°C main for each multisegment fragments, 46, 80, 229 respectively. Debye shielding low, dynamics short even physiological nearly as fully extended weakly bending rods lengths ratios. 85 mM, reduced 20–50% which suggests salt conditions 2–4-segment-long exhibit significant thermally induced flexing. Provided serve model native spectrin, implies that, overall conformational containing 20–40 flexible polymer.