ecoli.processes.chemotaxis.chemoreceptor_cluster
Chemoreceptor Cluster
This ReceptorCluster Process models the activity of a chemoreceptor cluster composed of Tsr and Tar amino acid chemoreceptors. The model is a Monod-Wyman-Changeux (MWC) model adapted from “Endres, R. G., & Wingreen, N. S. (2006). Precise adaptation in bacterial chemotaxis through assistance neighborhoods”. Each receptor homodimer is modeled as a two-state system (on or off) with energy values based on ligand concentration and methylation levels. This results in four energy levels: 1) on without ligand, on with ligand, off without ligand, off with ligand. Sensory adaptation comes from the methylation of receptors, which alters the free-energy offset and transition rate to favor the on state; attractant ligand binding favors the off state.
- class ecoli.processes.chemotaxis.chemoreceptor_cluster.ReceptorCluster(parameters=None)[source]
Bases:
Process
Models the activity of a chemoreceptor cluster
internal: Expects a store with ‘chemoreceptor_activity’, ‘CheR’, ‘CheB’, ‘CheB_P’, and ‘n_methyl’.
external: Expects a store with the ligand.
- Parameters:
parameters –
A dictionary of configuration options. The following configuration options may be provided:
ligand_id (
str
): The name of the external ligand sensed by the cluster.initial_ligand (
float
): The initial concentration of the ligand. The initial state of the cluster is set to steady state relative to this concetnration.n_Tar (
int
): number of Tar receptors in a clustern_Tsr (
int
): number of Tsr receptors in a clusterK_Tar_off (
float
): (mM) MeAsp binding by Tar (Endres06)K_Tar_on (
float
): (mM) MeAsp binding by Tar (Endres06)K_Tsr_off (
float
): (mM) MeAsp binding by Tsr (Endres06)K_Tsr_on (
float
): (mM) MeAsp binding by Tsr (Endres06)k_meth (
float
): Catalytic rate of methylationk_demeth (
float
): Catalytic rate of demethylationadapt_rate (
float
): adaptation rate relative to wild-type. cell-to-cell variation cause by variability in CheR and CheB
Note
dissociation constants (mM)
K_Tar_on = 12e-3 # Tar to Asp (Emonet05)
K_Tar_off = 1.7e-3 # Tar to Asp (Emonet05)
(Endres & Wingreen, 2006) has dissociation constants for serine binding, NiCl2 binding
-
defaults: Dict[str, Any]
{ 'K_Tar_off': 0.02, 'K_Tar_on': 0.5, 'K_Tsr_off': 100.0, 'K_Tsr_on': 10000000.0, 'adapt_rate': 1.2, 'initial_internal_state': { 'CheB': 0.00028, 'CheB_P': 0.0, 'CheR': 0.00016, 'chemoreceptor_activity': 0.3333333333333333, 'n_methyl': 2.0}, 'initial_ligand': 5.0, 'k_demeth': 0.0714, 'k_meth': 0.0625, 'ligand_id': 'MeAsp', 'n_Tar': 6, 'n_Tsr': 12}
- name = 'chemoreceptor_cluster'
- ecoli.processes.chemotaxis.chemoreceptor_cluster.get_brownian_ligand_timeline(environment_port=('external',), ligand_id='MeAsp', initial_conc=0.01, total_time=10, timestep=1, base=1.0003, speed=14)[source]
- ecoli.processes.chemotaxis.chemoreceptor_cluster.get_exponential_random_timeline(config)[source]
get timeline with random walk in exponential space
- ecoli.processes.chemotaxis.chemoreceptor_cluster.get_pulse_timeline(ligand='MeAsp')[source]
get a timeline with pulses applied to the external ligand
- ecoli.processes.chemotaxis.chemoreceptor_cluster.plot_receptor_output(output, settings, out_dir='out', filename='response')[source]