PHusis Therapeutics | Technology

PH-Domains

The PH (pleckstrin homology) domain is a 100 to 120 amino acid, protein superfold with a highly conserved 3 dimensional organization found in over 40 human proteins important in a number of human diseases including inflammation, cardiovascular disease, diabetes, Alzheimer’s disease and cancer.

The core of each PH-domain consists of seven highly conserved α-strands and a C-terminal β-helix. During signaling the PH domain binds to specific membrane phosphatidylinositol (PIP) lipids involved in intracellular signaling.

PHusis analysis of the PH-domain crystal structures show there is little primary sequence homology between the different PH-domains, yet alignment of secondary protein structure reveals high homology and conservation of the critical PIP binding residues. The hypervariable loop of the PH-domain allows for selectivity in the binding of small molecules thus, providing PHusis druggable and selective targets for cancer drug development.

PHT-427 compound

The PH-domain for modeling. The docking robustness of our PHuDock platform has been enhanced by the Schrödinger suite. In this picture, the X-Ray co-crystal substrate (IP4 magenta sticks) of a PH domain protein has been re-docked using the GLIDE extra precision (XP) mode. The best scored pose (green sticks) superposes almost identically to the X-Ray pose (magenta sticks); showing the remarkable accuracy in docking predictions that we can achieve. Docking predictions are one of the main approaches used in our drug-discovery platform.

PHT-427 compound

Below: Multiple sequence alignment of the PH domain of several PH-domains. The alignment shows conserved and similar amino acids (in color) and the non-conserved residues (no color); as well as a consensus plot (bars) that shows the recurrence of particular amino acids for this selected group).

PHusis Therapeutics PH domains

Left: A 3D overlay of the same proteins. On the above panel a 3-D superposition of PH domain proteins that have been crystallized. Blue shows spatial displacements from the mean of less than 3 Å, yellow and orange between 3 and 5 Å, and red, over 5 Å. A co-crystallized substrate (IP4) has been included (green and orange) to show the variable loop that enclose the PH domain active sites.