Transient non-native hydrogen bonds promote activation of a signaling protein.
Phosphorylation is a common mechanism for activating proteins within signaling pathways. Yet, the molecular transitions between the inactive and active conformational states are poorly understood. Here we quantitatively characterize the free-energy landscape of activation of a signaling protein, nitrogen regulatory protein C (NtrC), by connecting functional protein dynamics of phosphorylation-dependent activation to protein folding and show that only a rarely populated, pre-existing active conformation is energetically stabilized by phosphorylation. Using nuclear magnetic resonance (NMR) dynamics, we test an atomic scale pathway for the complex conformational transition, inferred from molecular dynamics simulations (Lei et al., 2009). The data show that the loss of native stabilizing contacts during activation is compensated by non-native transient atomic interactions during the transition. The results unravel atomistic details of native-state protein energy landscapes by expanding the knowledge about ground states to transition landscapes.
Gardino
Alexandra K
AK
Department of Biochemistry and Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02452, USA.
Villali
Janice
J
Kivenson
Aleksandr
A
Lei
Ming
M
Liu
Ce Feng
CF
Steindel
Phillip
P
Eisenmesser
Elan Z
EZ
Labeikovsky
Wladimir
W
Wolf-Watz
Magnus
M
Clarkson
Michael W
MW
Kern
Dorothee
D
D001419:Bacteria / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry*; D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D051922:PII Nitrogen Regulatory Proteins / Q000378:metabolism*; D011487:Protein Conformation; D013816:Thermodynamics
D001426:Bacterial Proteins; D051922:PII Nitrogen Regulatory Proteins