Adaptation Dynamics in Densely Clustered Chemoreceptors
Figure 1
Adaptation reactions on the chemoreceptor lattice.
(A) Bacterial chemoreceptors assemble into trimers of dimers that organize to form a dense hexagonal lattice. Most chemoreceptors have tether and modification sites. In the model, the assistance neighborhood for a given receptor (red) consists of all the receptors accessible by its tether, here taken to be the six nearest dimers (light red) in addition to itself. Groups of six receptor dimers switch cooperatively between active (blue) and inactive (white) states according to a MWC model. (B) Modeled reactions between CheR and the chemoreceptors with corresponding rates. Binding rates to the modification site depend on the receptor activity a. CheR in the cytoplasmic bulk may bind either the tether or modification site of a receptor (blue arrows, rates and
respectively). Once bound to the tether or modification site it may respectively bind the modification site or tether of itself (red arrows, rates
and
respectively) or any other receptor within its assistance neighborhood (green arrows, rate
to bind the neighboring modification site and rate
to bind the neighboring tether). Black arrows denote unbinding and catalytic steps (catalytic rate kr; tether unbinding rate
; modification site unbinding rate
). CheB-P participates in analogous reactions. In the rates, superscripts m and t denote binding to the modification site and tether site, respectively. The subscripts r and b denote CheR and CheB reactions, respectively.