4P18

Crystal Structure of frog M ferritin mutant D80K

Summary for 4P18

• Entry DOI: 10.2210/pdb4p18/pdb
• Descriptor: Ferritin, middle subunit, SULFATE ION, 1,2-ETHANEDIOL, ... (6 entities in total)
• Functional Keywords: oxidoreductase, ferroxidase, point mutation, intersubunit electrostatic interactions, frog-m ferritin mutant d80k
• Biological source: Rana catesbeiana (American bullfrog)
• Total number of polymer chains: 24
• Total formula weight: 502078.73

Authors

Pozzi, C.,Di Pisa, F.,Mangani, S.,Bernacchioni, C.,Ghini, V.,Turano, P. (deposition date: 2014-02-25, release date: 2014-10-01, Last modification date: 2023-09-27)

Primary citation

Bernacchioni, C.,Ghini, V.,Pozzi, C.,Di Pisa, F.,Theil, E.C.,Turano, P.
Loop electrostatics modulates the intersubunit interactions in ferritin.
Acs Chem.Biol., 9:2517-2525, 2014

PubMed Abstract: Functional ferritins are 24-mer nanocages that self-assemble with extended contacts between pairs of 4-helix bundle subunits coupled in an antiparallel fashion along the C2 axes. The largest intersubunit interaction surface in the ferritin nanocage involves helices, but contacts also occur between groups of three residues midway in the long, solvent-exposed L-loops of facing subunits. The anchor points between intersubunit L-loop pairs are the salt bridges between the symmetry-related, conserved residues Asp80 and Lys82. The resulting quaternary structure of the cage is highly soluble and thermostable. Substitution of negatively charged Asp80 with a positively charged Lys in homopolymeric M ferritin introduces electrostatic repulsions that inhibit the oligomerization of the ferritin subunits. D80K ferritin was present in inclusion bodies under standard overexpressing conditions in E. coli, contrasting with the wild type protein. Small amounts of fully functional D80K nanocages formed when expression was slowed. The more positively charged surface results in a different solubility profile and D80K crystallized in a crystal form with a low density packing. The 3D structure of D80K variant is the same as wild type except for the side chain orientations of Lys80 and facing Lys82. When three contiguous Lys groups are introduced in D80KI81K ferritin variant the nanocage assembly is further inhibited leading to lower solubility and reduced thermal stability. Here, we demonstrate that the electrostatic pairing at the center of the L-loops has a specific kinetic role in the self-assembly of ferritin nanocages.

PubMed: 25148224
DOI: 10.1021/cb500431r

Experimental method

X-RAY DIFFRACTION (1.91 Å)