Extended subnanosecond structural dynamics of myoglobin revealed by Laue crystallography

被引:95
作者
Bourgeois, D
Vallone, B
Arcovito, A
Sciara, G
Schotte, F
Anfinrud, PA
Brunori, M
机构
[1] Univ Roma La Sapienza, Dipartimento Sci Biochim, I-00185 Rome, Italy
[2] Univ Roma La Sapienza, Ist Pasteur Fondazione Cenc Bolognetti, I-00185 Rome, Italy
[3] Univ Grenoble 1, CEA, CNRS UMR 5075, Inst Biol Struct, F-38027 Grenoble 1, France
[4] European Synchrotron Radiat Facil, F-38043 Grenoble, France
[5] NIDDKD, Chem Phys Lab, NIH, Bethesda, MD 20892 USA
关键词
heme proteins; conformational landscape; packing defects; functional control;
D O I
10.1073/pnas.0508880103
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Work carried out over the last 30 years unveiled the role of structural dynamics in controlling protein function. Cavity networks modulate structural dynamics trajectories and are functionally relevant; in globins they have been assigned a role in ligand migration and docking. These findings raised renewed interest for time-resolved structural investigations of myoglobin (Mb), a simple heme protein displaying a photosensitive iron-ligand bond. Photodissociation of MbCO generates a nonequilibrium population of protein structures relaxing over a time range extending from picoseconds to milliseconds. This process triggers ligand migration to matrix cavities with clear-cut effects on the rate and yield of geminate rebinding. Here, we report subnanosecond time-resolved Laue diffraction data on the triple mutant YQR-Mb [Leu-29(1310)Tyr, His-64(E7)Gln, Thr-67(E10)Arg] that depict the sequence of structural events associated with heme and protein relaxation from 100 ps to 316 ns and above. The photodissociated ligand rapidly (< 0.1 ns) populates the Xe-binding cavity distal to the heme. Moreover, the heme relaxation toward the deoxy configuration is heterogeneous, with a slower phase (approximate to ns) evident in these experiments. Damping of the heme response appears to result from a strain exerted by the E-helix via the CD-turn; Phe-43(CD1), in close contact with heme, opposes tilt until the strain is relieved. A comparison with crystallographic data on wild-type Mb and mutants Leu(29)Phe or Leu(29)Trp suggests that the internal structure controls the rate and amplitude of the relaxation events. A correlation between structural dynamics as unveiled by Laue crystallography and functional properties of Mb is presented.
引用
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页码:4924 / 4929
页数:6
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