“...The physical and biochemical investigations of a new class of iron-sulfur proteins that contain a CDGSH iron sulfur binding domain.”
University of California, San Diego

Mark Paddock, Ph.D University of California, San Diego

Unique Structure of the NEET proteins

In an effort to understand the structural properties of the outer mitochondrial membrane protein mitoNEET, I crystallized a soluble form of the human protein in an orthorhombic space group. The structure was determined by X-ray diffraction from 1.5 Å resolution data collected from SSRL. To our surprise, the crystal structure showed that mitoNEET folds into a unique homodimeric structure with one 2Fe-2S cluster bound to each monomer within the dimer (see Figure below). A structural similarity search revealed that this fold is novel when compared with the > 700 known Fe-S proteins, and, furthermore, it is also unique when compared with the > 68,000 known members of the structural databases. In addition to the unique overall fold, the structure shows the unique 3Cys-1His coordination of the 2Fe-2S centers and an unusual distribution of hydrophobic and charged amino acid side chains. The crystal structure of the human paralog Miner1 was also determined. Mis-splicing of CISD2, which codes for Miner1, is causative in Wolfram Syndrome 2 (WFS2) resulting in early onset optic atrophy, diabetes mellitus, deafness and decreased lifespan. In knock-out studies, disruption of CISD2 leads to accelerated aging, blindness and muscle atrophy. The soluble region of human Miner1, solved to a resolution of 2.1 Å (R-factor=17%), showed that it has a similar protein fold to mitoNEET with two redox-active 2Fe-2S centers, each bound by a rare 3Cys-1His motif. Miner1 is the first functionally different protein that shares the NEET fold with its recently identified paralog mitoNEET, an outer mitochondrial membrane protein.