TABLE 2

Affinities of peptides 1 to 4 for wild-type BRS-3, BRS-3*, wild-type GRPR, and extracellular chimeric BRS-3s and GRPRs

Results are calculated from the data in Figs. 1 and 2 as described under Materials and Methods. eC2, e3, and e4 refer to the extracellular domain of the indicated receptor replacing the comparable domain of BRS-3* or GRPR as indicated.

IC50
 Peptide 4
Peptide 3
Peptide 2
Peptide 1
μM
BRS-3 0.49 ± 0.1 0.04 ± 0.01 0.0048 ± 0.0009 0.0027 ± 0.0001
BRS-3* 1.3 ± 0.1 0.08 ± 0.01 0.0033 ± 0.0009 0.0022 ± 0.0002
GRPR >>100 2.8 ± 0.1 0.200 ± 0.004 0.0009 ± 0.0001
Extracellular chimeras (loss-of-affinity)
    [e2-GRPR]BRS-3* 33.1 ± 1.2a 0.34 ± 0.03a 0.002 ± 0.001 0.0007 ± 0.0001
    [e3-GRPR]BRS-3* 1.7 ± 0.1 0.85 ± 0.04a 0.0120 ± 0.0001a 0.0025 ± 0.0001
    [e4-GRPR]BRS-3* 1.2 ± 0.1 0.06 ± 0.01 0.0009 ± 0.0001 0.0009 ± 0.0001
Extracellular chimeras (gain-of-affinity)
    [e2-BRS-3]GRPR 6.9 ± 0.2b 0.91 ± 0.07b 0.200 ± 0.009 0.0007 ± 0.0001
    [e3-BRS-3]GRPR >>100 >>100b 0.021 ± 0.001b 0.0027 ± 0.0004
    [e4-BRS-3]GRPR
>>100
3.0 ± 0.1
0.200 ± 0.007
0.0008 ± 0.0001

  • ↵ a P < 0.0001 lower affinity than the wild-type BRS-3* receptor.

  • ↵ b P < 0.001 higher affinity than the wild-type GRPR receptor.