Ultrafast proteinquake dynamics in cytochrome c.
We report here our systematic studies of the heme dynamics and induced protein conformational relaxations in two redox states of ferric and ferrous cytochrome c upon femtosecond excitation. With a wide range of probing wavelengths from the visible to the UV and a site-directed mutation we unambiguously determined that the protein dynamics in the two states are drastically different. For the ferrous state the heme transforms from 6-fold to 5-fold coordination with ultrafast ligand dissociation in less than 100 fs, followed by vibrational cooling within several picoseconds, but then recombining back to its original 6-fold coordination in 7 ps. Such impulsive bond breaking and late rebinding generate proteinquakes and strongly perturb the local heme site and shake global protein conformation, which were found to completely recover in 13 and 42 ps, respectively. For the ferric state the heme however maintains its 6-fold coordination. The dynamics mainly occur at the local site, including ultrafast internal conversion in hundreds of femtoseconds, vibrational cooling on the similar picosecond time scale, and complete ground-state recovery in 10 ps, and no global conformation relaxation was observed.
Zang
Chen
C
Department of Physics, Program of Biophysics, The Ohio State University, 191 West Woodruff Avenue, Columbus, Ohio, 43210, USA.
Stevens
Jeffrey A
JA
Link
Justin J
JJ
Guo
Lijun
L
Wang
Lijuan
L
Zhong
Dongping
D
D000818:Animals; D045304:Cytochromes c / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D006736:Horses; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D010782:Photolysis; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry
D005290:Ferric Compounds; D005296:Ferrous Compounds; D006418:Heme; D010649:Phenylalanine; D014364:Tryptophan; D045304:Cytochromes c