Sandbox 1498

3BPU is a transferase found in Homo sapiens. It is the 3rd PDZ domain of human membrane associated guanylate kinase Q96QZ7, C677S and C709S double mutant. It is encoded by the MAGI1 gene. [1]

Nature

Transferase

3BPU is a transferase, so it is an enzyme which catalyse reaction. 3BPU takes part of the family of MAGUK proteins, their role is to catalyze the formation of multiprotein complexes on the inner surface of the plasma in the junction region between two cells.

Membrane protein

3BPU is a peripheral membrane protein. These are specific, they interact with the integral membrane proteins and they penetrate into the peripheral membrane made of lipid bilayers. Their reversible attachment to the membrane permits to play the role of signaling into the cell or between cells and many other phenomena. In fact, the modification of its conformation triggers rearrangement, dissociation or change, and then a cascade of regulation. These proteins are usually interacting with lipids via non specific and hydrophobic interactions; for instance, here, 3BPU is made of hydrophobic amino-acids on the surface. But also electrostatic interactions (thanks to charged or/and polar amino-acids), Van der Waals and hydrogen bonds. But for 3PBU there is no hydrogen so nor hydrogen bonds.

Function

3BPU is involved in the cell signalisation. It may play a role as a scaffolding protein at cell-cell junctions. It may regulate acid-induced ASIC3^[1] currents by modulating its expression at the cell surface through interacting with its PDZ domain. It may also allow the interaction of Q96QZ7 with JAM4, providing an adhesion machinery at tight junctions. This may regulate the permeability of kidney glomerulus and small intestinal epithelial cells.^[2]

Structure

3BPU is mainly made of components which lead to hydrophobic and polar (charged or uncharged) interactions [2]

Primary structure

3BPU is a one chain structure of 88 amino-acids. There are 88 residues. [3]

Secondary structure

3BPU's structure is composed of 10% of (1 left-handed alpha helix; 9 residues, mainly Leu, Met, His, Glu, Gln) and 40% of (8 antiparallel strands; 36 residues, mainly Val, Ile, Trp).

Tertiary structure

3BPU is a membrane-associated protein. It interacts with the membrane thanks to its hydrophobic through hydrophobic interactions.

Interactions with ligands

3BPU's ligands are two Zn atoms.[4] The i are polar interactions. His645 and Glu714 interact with a first Zn atom. His699 and Val703 interact with a second Zn atom.

References

1. ↑ http://www.rcsb.org/pdb/protein/Q9UHC3
2. ↑ https://www.uniprot.org/citations/12773569