Table 1 Summary of binding parameters for the arrestin/OpsP/ATR complex.

From: Distinct loops in arrestin differentially regulate ligand binding within the GPCR opsin

Method

ATR titrations*

Arrestin titrations †

 

Apparent K d (μM)

Stoichiometry (receptors per ATR) ‡

Apparent K d (μM)

Stoichiometry (receptors per arrestin) §

Stoichiometry (receptors per ATR) ║

Arrestin pull down

4.8

2.4 (2.0)

0.13

1.3

NA

Acid trapping

2.8

2.5 (2.1)

0.14

1.6

2.2

Regeneration

3.5

2.0 (1.8)

0.053

1.4

2.3

  1. ATR, all-trans-retinol; NA, not applicable; OpsP, phosphorylated opsin.
  2. *Titrations were performed against 4 μM OpsP + 4 μM arrestin as described in Fig. 3a.
  3. †Titrations were performed against 4 μM OpsP + 40 μM ATR as described in Fig. 3b.
  4. ‡Derived from the maximal amplitude of the fitted curve (equation 1). The value derived from the two-site binding model (equation 2) is shown in parentheses.
  5. §Derived from the arrestin concentration at which binding saturation was reached (equation 3).
  6. ║Derived from the final amplitude of the fitted curve (equation 3).
  7. ¶Measured in isotonic buffer. All other experimental data in this table were obtained in the absence of salt.
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