STRUCTURE OF THE PROTEOLYTIC DOMAIN OF THE HUMAN MITOCHONDRIAL LON PROTEASE
[LONM_HUMAN] ATP-dependent serine protease that mediates the selective degradation of misfolded, unassembled or oxidatively damaged polypeptides as well as certain short-lived regulatory proteins in the mitochondrial matrix. May also have a chaperone function in the assembly of inner membrane protein complexes. Participates in the regulation of mitochondrial gene expression and in the maintenance of the integrity of the mitochondrial genome. Binds to mitochondrial promoters and RNA in a single-stranded, site-specific, and strand-specific manner. May regulate mitochondrial DNA replication and/or gene expression using site-specific, single-stranded DNA binding to target the degradation of regulatory proteins binding to adjacent sites in mitochondrial promoters. Endogenous substrates include mitochondrial steroidogenic acute regulatory (StAR) protein.[HAMAP-Rule:MF_03120]   
Publication Abstract from PubMed
ATP-dependent proteases are crucial for cellular homeostasis. By degrading short-lived regulatory proteins, they play an important role in the control of many cellular pathways and, through the degradation of abnormally misfolded proteins, protect the cell from a buildup of aggregates. Disruption or disregulation of mammalian mitochondrial Lon protease leads to severe changes in the cell, linked with carcinogenesis, apoptosis, and necrosis. Here we present the structure of the proteolytic domain of human mitochondrial Lon at 2 A resolution. The fold resembles those of the three previously determined Lon proteolytic domains from Escherichia coli, Methanococcus jannaschii, and Archaeoglobus fulgidus. There are six protomers in the asymmetric unit, four arranged as two dimers. The intersubunit interactions within the two dimers are similar to those between adjacent subunits of the hexameric ring of E. coli Lon, suggesting that the human Lon proteolytic domain also forms hexamers. The active site contains a 3(10) helix attached to the N-terminal end of alpha-helix 2, which leads to the insertion of Asp852 into the active site, as seen in M. jannaschii. Structural considerations make it likely that this conformation is proteolytically inactive. When comparing the intersubunit interactions of human with those of E. coli Lon taken with biochemical data leads us to propose a mechanism relating the formation of Lon oligomers with a conformational shift in the active site region coupled to a movement of a loop in the oligomer interface, converting the proteolytically inactive form seen here to the active one in the E. coli hexamer.
Structure of the catalytic domain of the human mitochondrial Lon protease: proposed relation of oligomer formation and activity.,Garcia-Nafria J, Ondrovicova G, Blagova E, Levdikov VM, Bauer JA, Suzuki CK, Kutejova E, Wilkinson AJ, Wilson KS Protein Sci. 2010 May;19(5):987-99. PMID:20222013
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.