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Table 1 Terms and definitions for allosteric synagics (see Figure 1)

From: Allosteric transition: a comparison of two models

Term Definition
orthoster primary ligand, binds at orthosteric (primary) receptor binding site and covers ligands as agonists, inverse agonists and (neutral) antagonists
alloster or allosteric modulator secondary ligand, binds to a non-overlapping (secondary or allosteric) binding site distinct from an orthosteric binding site
ago-alloster an alloster which can activate the receptor even in the absence of an orthoster, but with ceiling for the increased activity
allo-agonism the effect of an ago-alloster
syn-alloster alloster, at high orthoster concentrations it can still lift the response further with ceiling;
allo-synergy or synergy the effect of syn-allosters, different from super-agonism
ago-syn-alloster alloster, both activates receptors in absence of orthoster and increases activity even at high orthoster concentration. Both increases in activity have ceiling
allo-ago-synergy the effect of ago-syn-allosters, different from super-agonism
enhancer alloster, moves orthoster d-r curves to the left with ceiling
allo-competitor alloster, moves orthoster d-r curves right with or without ceiling
allo-mixed-competitor alloster, decreases activity and changes apparent affinity constants for orthosters. Orthoster d-r curves with allo-mixed-competitor are right-shifted but may have increased affinity
enhancer-inhibitor alloster that both increases apparent affinity constants and decreases activity for orthosters. With enhancer-inhibitor, orthoster d-r curves move left with ceiling
ago-inverse-alloster alloster, stimulates activity from an allosteric site in its own right, but with an activity which is reduced with increasing orthoster concentrations
ortho-alloster or bitopic ligand compound with moieties for simultaneous binding and activation at both orthosteric and allosteric receptor binding sites
synagics the study of equilibrium and steady-state concentration-responses of ligand interactions with receptive units such as protein macromolecules
positive and negative allosteric modulators (PAMs* and NAMs**) - ligands that increase or decrease receptor activity directly or indirectly from an allosteric binding site.
  1. *PAMs cover both ago-allosters, syn-allosters, and ago-syn-allosters. Enhancers may be included here. ** NAMs cover both allo-mixed-competitors, enhancer-inhibitors, and ago-inverse-allosters. Allo-competitors may be included here.