Volume 12, Issue 11, Pages 1245-1252 (November 2005) The Binding of Human Carbonic Anhydrase II by Functionalized Folded Polypeptide Receptors  Theresa Andersson, Martin Lundquist, Gunnar T. Dolphin, Karin Enander, Bengt-Harald Jonsson, Jonas W. Nilsson, Lars Baltzer  Chemistry & Biology  Volume 12, Issue 11, Pages 1245-1252 (November 2005) DOI: 10.1016/j.chembiol.2005.08.018 Copyright © 2005 Elsevier Ltd Terms and Conditions

Figure 1 Scaffold Sequences The sequences of the scaffold polypeptides KE2 and TA4. Residues that differ between the sequences are shown in boldface. In both sequences, the ligand was attached to the side chain of Lys-34, and the fluorescent dansyl group was attached to the side chain of Lys-15. In the peptide KE-Q, no ligand was incorporated, and a fluorescent dabcyl group was attached to the side chain of Lys-15. Norleucines are designated as “J.” Chemistry & Biology 2005 12, 1245-1252DOI: (10.1016/j.chembiol.2005.08.018) Copyright © 2005 Elsevier Ltd Terms and Conditions

Figure 2 Identification of Binding Site Overlay of HSQC spectra of 50 μM 15N-labeled HCAII in aqueous solution at pH 7 and of 50 μM 15N-labeled HCAII in the presence of 50 μM KE2-D(15)-6. Red crosspeaks are from free HCAII, blue crosspeaks are from the 1:1 mixture, and some peaks show a lack of overlap due to complexation with the receptor molecule. Chemistry & Biology 2005 12, 1245-1252DOI: (10.1016/j.chembiol.2005.08.018) Copyright © 2005 Elsevier Ltd Terms and Conditions

Figure 3 Efficient Binding of HCAII by Functionalized Helix-Loop-Helix Receptors Is Manifested by Strong Perturbations of the HCAII Surface Illustration of binding of HCAII by KE2-D(15)-6 and by KE2-D(15)-8, in which the amide nitrogens of residues perturbed by complexation are shown in space-filling mode. Yellow nitrogens show residues that are affected by both receptors, residues affected by KE2-D(15)-8, but not by KE2-D(15)-6, are shown in red, and residues affected only by KE2-D(15)-6 are shown in blue. The shorter spacer of KE2-D(15)-6 causes larger perturbations of the target protein than does that of KE2-D(15)-8. A shift is registered if the chemical shift is changed by 10 Hz or more. The figure was prepared by using the program MOLMOL [18]. Inset: As an illustration of the relative sizes of HCAII and the scaffold, a modeled structure of TA4 is compared to that of the crystal structure of HCAII. Chemistry & Biology 2005 12, 1245-1252DOI: (10.1016/j.chembiol.2005.08.018) Copyright © 2005 Elsevier Ltd Terms and Conditions

Figure 4 Binding of HCAII by a Long-Spacered Receptor Illustration of binding of KE2-D(15)-11 to HCAII, in which the amide nitrogens of residues perturbed by complexation are shown in space-filling mode. A shift is registered if the chemical shift is changed by 10 Hz or more. The figure was prepared by using the program MOLMOL [18]. Chemistry & Biology 2005 12, 1245-1252DOI: (10.1016/j.chembiol.2005.08.018) Copyright © 2005 Elsevier Ltd Terms and Conditions

Figure 5 Scaffold Binding Is Not Optimal in TA4-D(15)-8 Illustration of binding of TA4 and of TA4-D(15)-8 to HCAII. The yellow nitrogens are those of residues affected by binding of both receptors, the red nitrogens are those of residues affected only by TA4, and the blue nitrogens are those affected only by TA4-D(15)-8. The binding site of TA4 is more distant from the active site of HCAII than that of TA4-D(15)-8, showing that, in the latter case, the scaffold does not, and probably cannot, bind in the site for which the 100 μM dissociation constant was measured. The Cut-off limit for a chemical shift change is 10 Hz. If a lower cut-off than 10 Hz is used for TA4 to compensate for the weaker binding, it nevertheless shows that the binding site of TA4 deviates significantly from that of TA4-D(15)-8. The figure was prepared by using the program MOLMOL [18]. Chemistry & Biology 2005 12, 1245-1252DOI: (10.1016/j.chembiol.2005.08.018) Copyright © 2005 Elsevier Ltd Terms and Conditions