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At least 487 records · Page 27Linked to original sources
PubMed2004

Molecular dynamics simulation of the C-terminal sterile alpha-motif domain of human p73alpha: evidence of a dynamical relationship between helices 3 and 5.

We used molecular dynamics simulation to evaluate the association properties of C-terminal sterile alpha-motif (SAM) domain of human p73alpha. To test the dimerization propensity of this structure we carried out four simulations: EphB2 X-ray dimer, p73 modeled dimer, p73 NMR monomer, and p73 modeled monomer with an elongated helix 5. The results show a direct interaction between helix 5 and helix 3 since a conformational collapse of helix 3 is observed when dimer contact and/or an elongation of helix 5 is introduced by modeling in p73 SAM domain. On the basis of these results we suggest that the recognition properties of the SAM domains may be modulated by the conformational state of helix 5.

Amino Acid Motifs↗
PubMed2006

Structural and dynamical properties of different protonated states of mutant HIV-1 protease complexed with the saquinavir inhibitor studied by molecular dynamics simulations.

To understand the basis of drug resistance, particularly of the HIV-1 PR, three molecular dynamics (MD) simulations of HIV-1 PR mutant species, G48V, complexed with saquinavir (SQV) in explicit aqueous solution with three protonation states, diprotonation on Asp25 and Asp25' (Di-pro) and monoprotonation on each Asp residue (Mono-25 and Mono-25'). For all three states, H-bonds between saquinavir and HIV-1 PR were formed only in the two regions, flap and active site. It was found that conformation of P2 subsite of SQV in the Mono-25 state differs substantially from the other two states. The rotation about 177 degrees from the optimal structure of the wild type was observed, the hydrogen bond between P2 and the flap residue (Val48) was broken and indirect hydrogen bonds with the three residues (Asp29, Gly27, and Asp30) were found instead. In terms of complexation energies, interaction energy of -37.3 kcal/mol for the Mono-25 state is significantly lower than those of -30.7 and -10.7kcal/mol for the Mono-25' and Di-pro states, respectively. It was found also that protonation at the Asp25 leads to a better arrangement in the catalytic dyad, i.e., the Asp25-Asp25' interaction energy of -8.8 kcal/mol of the Mono-25 is significantly lower than that of -2.6kcal/mol for the Mono-25' state. The above data suggest us to conclude that interaction in the catalytic area should be used as criteria to enhance capability in drug designing and drug screening instead of using the total inhibitor/enzyme interaction.

Binding Sites↗
PubMedDate not supplied

Treatment of midclavicular nonunion: comparison of dynamic compression plating and low-contact dynamic compression plating techniques.

In this study a comparison of patients with midclavicular nonunion, treated by a combination of internal fixation with dynamic compression plate (DCP) or low-contact DCP (LC-DCP) and application of autogenous corticocancellous chips or sculptured graft on nonunion areas, was performed. Time to union in the patients treated with LC-DCP fixation was shorter than in those treated with DCP fixation (P <.001). Union was obtained in all patients treated with LC-DCP fixation and in 87.5% of those treated with DCP fixation. All of those treated with LC-DCP fixation returned to their original jobs, whereas two patients treated with DCP fixation had to change jobs. According to the Disabilities of the Arm, Shoulder, and Hand functional score, at the last follow-up visit, functional outcomes of the patients treated with LC-DCP fixation were more satisfactory (P <.001). The addition of internal fixation of the clavicle with DCP or LC-DCP to application of autogenous corticocancellous chips, or sculptured graft on nonunion areas in patients with midclavicular nonunion, shortens the time to union, increases union rates, and provides satisfactory functional outcomes.

Adult↗
PubMed2005

Dynamic control of ocular disaccommodation: first and second-order dynamics.

Velocity and acceleration characteristics provide valuable information about dynamic control of accommodation. We investigated velocity and acceleration of disaccommodation (near-far focusing) from three starting positions. Peak velocity and peak acceleration of disaccommodation increased with the proximity of starting position however for a given starting position they were invariant of response magnitude. These results suggest that all disaccommodation responses are initiated towards a constant primary destination and are switched mid-flight to attain the desired final position. Large discrepancies between the primary destination and desired final position appear to produce overshoots and oscillations of small responses from proximal starting positions.

Accommodation, Ocular↗
PubMed2003

Conformational dynamics of the F1-ATPase beta-subunit: a molecular dynamics study.

According to the different nucleotide occupancies of the F(1)-ATPase beta-subunits and due to the asymmetry imposed through the central gamma-subunit, the beta-subunit adopts different conformations in the crystal structures. Recently, a spontaneous and nucleotide-independent closure of the open beta-subunit upon rotation of the gamma-subunit has been proposed. To address the question whether this closure is dictated by interactions to neighbored subunits or whether the open beta-subunit behaves like a prestressed "spring," we report multinanosecond molecular dynamics simulations of the isolated beta-subunit with different start conformations and different nucleotide occupancies. We have observed a fast, spontaneous closure motion of the open beta(E)-subunit, consistent with the available x-ray structures. The motions and kinetics are similar to those observed in simulations of the full (alpha beta)(3)gamma-complex, which support the view of a prestressed "spring," i.e., that forces internal to the beta(E)-subunit dominate possible interactions from adjacent alpha-subunits. Additionally, nucleotide removal is found to trigger conformational transitions of the closed beta(TP)-subunit; this provides evidence that the recently resolved half-closed beta-subunit conformation is an intermediate state before product release. The observed motions provide a plausible explanation why ADP and P(i) are required for the release of bound ATP and why gamma-depleted (alpha beta)(3) has a drastically reduced hydrolysis rate.

Adenosine Diphosphate↗
PubMed1989

Dynamic imaging of lateral diffusion by electron spin resonance and study of rotational dynamics in model membranes. Effect of cholesterol.

The effects of cholesterol on the dynamics and the structural properties of two different spin probes, the sterol type CSL and the phospholipid type 16-PC, in POPC/cholesterol oriented multilayer model membranes were examined. Our results are consistent with a nonideal solution containing cholesterol-rich clusters created by the self association of cholesterol in POPC model membranes. The lateral diffusion coefficient D of the spin probes was measured over the temperature range of 15 to 60 degrees C and over the concentration range of 0 to 30 mol% of cholesterol in the model membrane by the electron spin resonance (ESR) imaging method. The rotational diffusion coefficients (including R perpendicular) and the order parameter S were determined utilizing a nonlinear least square ESR spectral simulation method. D, R perpendicular and S of CSL deviate considerably from linear dependence on mole percent cholesterol. The D of CSL was decreased by a factor of four at 15 degrees C and a factor of two at 60 degrees C for concentrations of cholesterol over 10 mol %, whereas those of 16-PC were hardly affected. Cholesterol decreased R perpendicular by a factor of 10 at 30 mol % of cholesterol, but it increased slightly that of 16-PC. A significant increase of S for CSL due to the presence of cholesterol was observed. It is shown how the difference in variation of S for CSL vs. 16-PC with composition may be interpreted in terms of their respective activity coefficients, and how a single universal linear relation is obtained for the S of both probes in terms of a scaled temperature. Simple but general correlations of D and of R perpendicular with S were also found, which aid in the interpretation of these diffusion coefficients.

Cholesterol↗
PubMed1997

Transmembrane helix structure, dynamics, and interactions: multi-nanosecond molecular dynamics simulations.

To probe the fundamentals of membrane/protein interactions, all-atom multi-nanosecond molecular dynamics simulations were conducted on a single transmembrane poly(32)alanine helix in a fully solvated dimyristoyphosphatidylcholine (DMPC) bilayer. The central 12 residues, which interact only with the lipid hydrocarbon chains, maintained a very stable helical structure. Helical regions extended beyond these central 12 residues, but interactions with the lipid fatty-acyl ester linkages, the lipid headgroups, and water molecules made the helix less stable in this region. The C and N termini, exposed largely to water, existed as random coils. As a whole, the helix tilted substantially, from perpendicular to the bilayer plane (0 degree) to a 30 degrees tilt. The helix experienced a bend at its middle, and the two halves of the helix at times assumed substantially different tilts. Frequent hydrogen bonding, of up to 0.7 ns in duration, occurred between peptide and lipid molecules. This resulted in correlated translational diffusion between the helix and a few lipid molecules. Because of the large variation in lipid conformation, the lipid environment of the peptide was not well defined in terms of "annular" lipids and on average consisted of 18 lipid molecules. When compared with a "neat" bilayer without peptide, no significant difference was seen in the bilayer thickness, lipid conformations or diffusion, or headgroup orientation. However, the lipid hydrocarbon chain order parameters showed a significant decrease in order, especially in those methylene groups closest to the headgroup.

Computer Simulation↗
PubMed1997

Influence of static and dynamic bends on the birefringence decay profile of RNA helices: Brownian dynamics simulations.

Bends in nucleic acid helices can be quantified in a transient electric birefringence (TEB) experiment from the ratio of the terminal decay times of the bent molecule and its fully duplex counterpart (tau-ratio method). The apparent bend angles can be extracted from the experimental tau-ratios through the application of static (equilibrium-ensemble) hydrodynamic models; however, such models do not properly address the faster component(s) of the birefringence decay profile, which can represent up to 80% of the total birefringence signal for large band angles. To address this latter issue, the relative amplitudes of the components in the birefringence decay profile have been analyzed through a series of Brownian dynamics (BD) simulations. Decay profiles have been simulated for three-, five-, and nine-bead models representing RNA molecules with central bends of 30 degrees, 60 degrees, and 90 degrees, and with various degrees of associated angle dispersion. The BD simulations are in close agreement with experimental results for the fractional amplitudes, suggesting that both amplitudes and terminal tau-ratios can be used as a measure of the magnitudes of bends in the helix axis. Although the current results indicate that it is generally not possible to distinguish between relatively fixed and highly flexible bends from single tau-ratio measurements, because they can lead to similar reductions in terminal decay time and amplitude, measurements of the dependence of the fractional amplitudes on helix length may afford such a distinction.

Algorithms↗
PubMed1997

Structure and dynamic properties of diunsaturated 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine lipid bilayer from molecular dynamics simulation.

Unsaturated fatty acid chains are known to be an essential structural part of biomembranes, but only monounsaturated chains have been included in the molecular dynamics (MD) simulations of membrane systems. Here we present a 1-ns MD simulation for a diunsaturated 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC; 16:0/18:2[delta9,12]) bilayer. The structural behavior of the phosphatidylcholine headgroup, the glycerol backbone, and the hydrating water were assessed and found to be consistent with the existing information about similar systems from both experimental and computational studies. Further analysis was focused on the structure of the double bond region and the effects of the diunsaturation on the bilayer interior. The behavior of the diunsaturated sn-2 chains is affected by the tilted beginning of the chain and the four main conformations of the double bond region. The double bonds of the sn-2 chains also influenced the characteristics of the saturated chains in the sn-1 position. Furthermore, extreme conformations of the sn-2 chains existed that are likely to be related to the functional role of the double bonds. The results here point out the importance of polyunsaturation for the biological interpretations deduced from the membrane MD simulations.

Biophysical Phenomena↗
PubMed1998

Dynamic properties of Na+ ions in models of ion channels: a molecular dynamics study.

We present simulation results for the effective diffusion coefficients of a sodium ion in a series of model ion channels of different diameters and hydrophobicities, including models of alamethicin, a leucine-serine peptide, and the M2 helix bundle of the nicotinic acetylcholine receptor. The diffusion coefficient, which in the simulations has a value of 0.15(2) A2ps-1 in bulk water, is found to be reduced to as little as 0.02(1) A2ps-1 in the narrower channels, and to about 0.10(5) A2ps-1 in wider channels such as the nicotinic acetylcholine receptor. It is anticipated that this work will be useful in connection with calculations of channel conductivity using such techniques as the Poisson-Nernst-Planck equation, Eyring rate theory, or Brownian dynamics.

Alamethicin↗
PubMed1999

Structure, interaction, dynamics and solvent effects on the DNA-EcoRI complex in aqueous solution from molecular dynamics simulation.

A 0.7-ns molecular dynamics simulation of the DNA-EcoRI complex in a 7.0-A solvent shell indicated a stable behavior of the system. No significant evaporation or smearing of the solvent's outer boundary occurred. The structure and the intermolecular interactions were found to be well maintained during the simulation. The interaction pattern in the simulation was found to be very similar to that in the crystal structure. Most of the specific interactions between the DNA and the protein were found to be enhanced in the simulation compared to that in the crystal structure as a result of improved interaction geometry. The nonspecific interactions were found to be stronger than the specific ones. The specific interactions between the N7 atoms of Gua(4) or Ade(5) or Ade(6) and the protein were found to be present over almost the entire time of the simulation, whereas hydrogen bonds involving the amino groups of the Ade(5) and Ade(6) with the protein were found to be relatively weaker, with lower probability and shorter lifetime. The time evolution of the root mean square deviations of the DNA and the protein were highly correlated even at the later part of the simulation, showing the tight binding between them. Several long-lived water bridges were found between the DNA backbone atoms and the protein and also between the two protein monomers, which increased the overall stability of the complex. The two protein monomers were found to interact strongly with each other. The energy of the DNA kink deformation was estimated as approximately 31 kcal/mol.

Binding Sites↗
PubMedDate not supplied

Dynamic versus static grip strength: how grip strength changes when the wrist is moved, and why dynamic grip strength may be a more functional measurement.

The synergistic relationship between wrist/forearm range of motion (ROM) and grip strength (GS) is arguably one of the most important aspects of hand function. Clinically, GS is measured with the wrist in a standardized static position, and the results of such tests have been deemed valid and reliable. The question remains, however, whether this static GS (SGS) measurement is an accurate indication of how an individual functionally grips objects--that is, most functional tasks require the fingers to grasp an object forcibly while moving the proximal joints such as the wrist and forearm. Therefore, further analysis of an individual's dynamic GS (DGS) during wrist/forearm movements may improve the clinician's understanding of hand function and provide more pertinent guidelines for assessing functional gripping, e.g., for vocational and avocational tasks and in designing workstations. The purpose of this study is twofold: to describe and assess a DGS testing device that utilizes optically encoded gyroscopes and a strain-gauge dynamometer to simultaneously measure GS and wrist/forearm position over real time; and to assess and compare grip force production differences in SGS and DGS in uninjured wrists, using this novel device. Twenty-nine uninjured wrists of men (n = 15) and women (n = 14)--age range, 21 to 43 years--were tested with the DGS device. Subjects were excluded if they had any previous wrist/forearm fracture, pain, or limitation of motion. The DGS device was designed and fabricated with two optically encoded gyroengines, a vertical gyroscope with two axes for measuring flexion/extension and radial/ulnar deviation, and a directional gyroscope with one axis for measuring supination/pronation, mounted on a strain-gauge dynamometer. The signals from the gyroscopes and dynamometer were processed by means of a data aquisition board and analog-to-digital circuitry and collected on a 486-MHz computer. The methods included repeated testing of each gyroscope axis to known angular measurements, and randomly assigned maximal gripping trials from the 29 subjects. The standard deviation of gyroengines is 1 degree to 2 degrees for each ROM axis. Maximal DGS is significantly less (mean 14%) than SGS, and SGS is 29% less than DGS at the same three-dimensional ROM positions. Gyroengines are feasible three-dimensional tracking devices that can be used to monitor wrist/forearm ROM in conjunction with GS.

Adult↗
PubMedDate not supplied

Contrast-enhanced high in-plane resolution dynamic MRI of the breast. Are there advantages in comparison to standard dynamic MRI?

OBJECTIVE: To evaluate the diagnostic advantages of high in-plane resolution contrast-enhanced (CE) magnetic resonance imaging (MRI) of the breast in comparison to standard CE-MRI. METHODS: Forty-one patients with 51 hypervascularized lesions were selected prospectively after undergoing bilateral standard CE MRI (slice thickness 4 mm, in-plane resolution 1.52 x 1.25 mm2, temporal resolution 81 s). Patients underwent high in-plane resolution CE MRI, either (n=21) a two-dimensional fast-low-angle-shot sequence (slice thickness 4 mm, in-plane resolution 0.76 x 0.63 mm2, temporal resolution 96 s) or (n=20) a SE sequence being used (slice thickness 4 mm, in-plane resolution 0.8 x 0.63 mm2, temporal resolution 115 s). RESULTS: Histopathology revealed 33 malignant and 18 benign lesions (0.2-2.2 cm). Morphologic characteristics were much better visualized with high in-plane resolution. Additional diagnostic information, however, resulted only in one patient with fibroadenoma due to a better visualization of smooth contours. CONCLUSIONS: High in-plane resolution provides better visualization of morphologic patterns in comparison to standard dynamic MRI. However, a diagnostic advantage is only rare.

Breast↗
PubMed2003

A dynamic structure for the acyl-enzyme species of the antibiotic aztreonam with the Citrobacter freundii beta-lactamase revealed by infrared spectroscopy and molecular dynamics simulations.

Infrared difference spectra show that at least 4 conformations coexist for the ester carbonyl group of the stable acyl-enzyme species formed between the antibiotic aztreonam and the class C beta-lactamase from Citrobacter freundii. A novel method for the assignment of the bands that arise from the ester carbonyl group has been employed. This has made use of the finding that the infrared absorption intensity of aliphatic esters is surprisingly constant, so a direct comparison with simple model esters has been possible. This has allowed a clear distinction to be made between ester and amide (protein) absorptions. The polarity of the conformer environment varies from hexane-like to strongly hydrogen-bonded. We assume that the conformer with the lowest frequency (1,690 cm(-)(1)) and hence the strongest hydrogen-bonding is the singular conformer observed in the X-ray crystallographic structure, since a good interaction via two hydrogen bonds with the oxyanion hole is seen. Molecular dynamics simulation by the method of locally enhanced sampling revealed that the motion of the ester carbonyl of the acyl-enzyme species in and out of the oxyanion hole is facile. The simulation revealed two pathways for this motion that would go through intermediates that first break one or the other of the two hydrogen bonds to the oxyanion hole, prior to departure of the carbonyl moiety out of the active site. It is likely that such motion for the acyl-enzyme species might also occur with more typical beta-lactam substrates for beta-lactamases, but their detection in the more rapid time scale may prove a challenge.

Acylation↗
PubMed2001

Structure and dynamics of self-assembling beta-sheet peptide tapes by dynamic light scattering.

Oligomeric peptides can be designed which undergo one-dimensional self-assembly in solution to form beta-sheet tapes a single molecule in thickness and micrometers in length.(1) In this paper, we present the first systematic investigation of the size, shape, dynamics, and interactions of beta-sheet tapes formed by a self-assembling 24-residue peptide, K24, in 2-chloroethanol, over a wide range of peptide concentrations c (c: 10(-7)-1 mM), using photon correlation spectroscopy. The tapes behave like semiflexible chains with persistence lengths of several hundred nanometers and much longer contour lengths, even at c approximately 0.1 nM. The polarized q-dependent light-scattering intensity I fits a model of a prolate object with major and minor axes alpha approximately 630 nm and beta approximately 40 nm. This is an unexpected result in view of the previous theoretical predictions that tapelike polymers could form oblate coinlike structures in solution.(2) This experimentally observed behavior is attributed to the pronounced twist and bend of the beta-tapes, which do not allow them to form the coinlike structures, but instead they favor the formation of elongated polymers. At c approximately 10(-2) mM, the tapes are seen to start overlapping and forming networks with unusually large mesh sizes (e.g., ca. 400 nm at 15 mciroM), much larger than those of conventional polymers. With increasing peptide concentration the mesh size decreases and the network becomes a physical gel at c approximately 0.4 mM. These semidilute solutions are characterized by one main relaxation mode associated with the cooperative diffusion of the entangled tape network, and a weaker slower mode, associated with gel cluster formation. The concentration dependence of xi (xi(c) approximately c(-0.34)) is much weaker compared to the expected scaling for Gaussian or swollen chains (xi(c) approximately c(-1) for Gaussian chains, or xi(c) approximately c(-3/4) for swollen ones), but is not inconsistent with the expected scaling for rigid rods. On the basis of the concentration dependencies of the light-scattering intensity I and of the cooperative diffusion coefficient D, the cooperative friction coefficient f(c) is found to display a stronger concentration dependence (f(c) approximately c(1.34)) than in the case of semidilute flexible and semiflexible polymer solutions (f(c) approximately c(0.5)).(3) Thus, we may conclude that the network of entangled tapes approximates in its behavior that of semirigid polymers.

Light↗
PubMed2003

Molecular dynamics simulation of the formation, structure, and dynamics of small phospholipid vesicles.

Here, we use coarse grained molecular dynamics (MD) simulations to study the spontaneous aggregation of dipalmitoylphosphatidylcholine (DPPC) lipids into small unilamellar vesicles. We show that the aggregation process occurs on a nanosecond time scale, with bicelles and cuplike vesicles formed at intermediate stages. Formation of hemifused vesicles is also observed at higher lipid concentration. With either 25% dipalmitoylphosphatidylethanolamine (DPPE) or lysoPC mixed into the system, the final stages of the aggregation process occur significantly faster. The structure of the spontaneously formed vesicles is analyzed in detail. Microsecond simulations of isolated vesicles reveal significant differences in the packing of the lipids between the inner and outer monolayers, and between PC, PE, and lysoPC. Due to the small size of the vesicles they remain almost perfectly spherical, undergoing very limited shape fluctuations or bilayer undulations. The lipid lateral diffusion rate is found to be faster in the outer than in the inner monolayer. The water permeability coefficient of the pure DPPC vesicles is of the order of 10(-)(3) cm s(-)(1), in agreement with experimental measurements.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2005

Electron spin dynamics as a probe of molecular dynamics: temperature-dependent magnetic field effects on charge recombination within a covalent radical ion pair.

The electron spin-spin exchange interaction, 2J, in radical pairs (RPs) is exquisitely sensitive to the details of molecular structure and can thus serve as an important probe of structural dynamics in RPs of potential interest to photonic and electronic devices. Photoinitiated ultrafast two-step charge separation produces (1)(MeOAn(+)(*)-6ANI-NI(-)(*)), where MeOAn = p-methoxyaniline, 6ANI = 4-(N-piperidinyl)naphthalene-1,8-dicarboximide, and NI = naphthalene-1,8:4,5-bis(dicarboximide). Radical pair intersystem crossing subsequently produces (3)(MeOAn(+)(*)-6ANI-NI(-)(*)), and the total RP population decays with approximately 10 ns lifetime at 140 K, which increases to nearly 30 ns at 300 K in toluene. The activation energy observed for this process is negative and can be explained by a mechanism involving a conformational preequilibrium of the RP followed by charge recombination. Over the same temperature range, the magnetic field effect (MFE) on yield of the triplet recombination product, MeOAn-6ANI-(3)()NI, yields the magnitude of 2J, which directly monitors the superexchange electronic coupling for charge recombination. A single resonance in the MFE plot is observed at 300 K, which splits into two resonances at temperatures below 230 K, suggesting that there are two distinct groups of RP conformations at low temperature. The magnitude of 2J for the lower field resonance (10 mT) at 140 K is 5 times smaller than that of the high field resonance. At 300 K the equilibrium is shifted almost entirely to the set of conformers with the stronger electronic coupling. The motion that couples these two groups of conformations is the motion that most effectively gates the donor-acceptor electronic coupling.

Journal Article↗
PubMed2005

Dynamic mechanism for the autophosphorylation of CheA histidine kinase: molecular dynamics simulations.

The two-component system (TCS) is an important signal transduction component for most bacteria. This signaling pathway is mediated by histidine kinases via autophosphorylation between P1 and P4 domains. Taking chemotaxis protein CheA as a model of TCS, the autophosphorylation mechanism of the TCS histidine kinases has been investigated in this study by using a computational approach integrated homology modeling, ligand-protein docking, protein-protein docking, and molecular dynamics (MD) simulations. Four nanosecond-scale MD simulations were performed on the free P4 domain, P4-ATP, P4-TNPATP, and P1-P4-ATP complexes, respectively. Upon its binding to the binding pocket of P4 with a folded conformation, ATP gradually extends to an open state with help from a water molecule. Meanwhile, ATP forms two hydrogen bonds with His413 and Lys494 at this state. Because of the lower energy of the folded conformations, ATP shrinks back to its folded conformations, leading to the rupture of the hydrogen bond between ATP and Lys494. Consequently, Lys494 moves away from the pocket entrance, resulting in an open of the ATP lid of P4. It is the open state of P4 that can bind tightly to P1, where the His45 of P1 occupies a favorable position for its autophosphorylation from ATP. This indicates that ATP is not only a phosphoryl group donor but also an activator for CheA phosphorylation. Accordingly, a mechanism of the autophosphorylation of CheA is proposed as that the ATP conformational switch triggers the opening of the ATP lid of P4, leading to P1 binding tightly, and subsequently autophosphorylation from ATP to P1.

Adenosine Triphosphate↗