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Lon Protease (lon + protease)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

The Membrane-Bound Lon Protease from Thermoplasma Displays Unfolding Activity

ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2006
Henrike Besche
The membrane-bound Lon protease from Thermoplasma acidophilum (Ta Lon) was shown to unfold and degrade a fusion of the green fluorescent protein with calmodulin (GFP,CaM). Unfolding and degradation were ATP-dependent reactions and could be inhibited by calcium ions, which are known to stabilize calmodulin. Notably, an inverse fusion of the same proteins, i.e., CaM,GFP, as well as GFP or GFP-SsrA, was neither unfolded nor degraded. Thus, Ta Lon seems to unfold and degrade preferentially protein substrates with an extended unstructured C-terminus. A set of Ta Lon variants mutated in critical residues of the AAA+ domain, were tested for their respective ATPase and GFP,CaM unfolding activity. This analysis revealed that the rate of ATP hydrolysis correlated with the efficiency of the GFP,CaM unfolding activity. In summary, we show here that the membrane-bound Ta Lon protease displays an unfolding activity, which is correlated with the rate of ATP hydrolysis. [source]

Structure of the N-terminal fragment of Escherichia coli Lon protease

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2010
Mi Li
The structure of a recombinant construct consisting of residues 1,245 of Escherichia coli Lon protease, the prototypical member of the A-type Lon family, is reported. This construct encompasses all or most of the N-terminal domain of the enzyme. The structure was solved by SeMet SAD to 2.6,Å resolution utilizing trigonal crystals that contained one molecule in the asymmetric unit. The molecule consists of two compact subdomains and a very long C-terminal ,-helix. The structure of the first subdomain (residues 1,117), which consists mostly of ,-strands, is similar to that of the shorter fragment previously expressed and crystallized, whereas the second subdomain is almost entirely helical. The fold and spatial relationship of the two subdomains, with the exception of the C-terminal helix, closely resemble the structure of BPP1347, a 203-amino-acid protein of unknown function from Bordetella parapertussis, and more distantly several other proteins. It was not possible to refine the structure to satisfactory convergence; however, since almost all of the Se atoms could be located on the basis of their anomalous scattering the correctness of the overall structure is not in question. The structure reported here was also compared with the structures of the putative substrate-binding domains of several proteins, showing topological similarities that should help in defining the binding sites used by Lon substrates. [source]

Slicing a protease: Structural features of the ATP-dependent Lon proteases gleaned from investigations of isolated domains

PROTEIN SCIENCE, Issue 8 2006
Tatyana V. Rotanova
Abstract ATP-dependent Lon proteases are multi-domain enzymes found in all living organisms. All Lon proteases contain an ATPase domain belonging to the AAA+ superfamily of molecular machines and a proteolytic domain with a serine-lysine catalytic dyad. Lon proteases can be divided into two subfamilies, LonA and LonB, exemplified by the Escherichia coli and Archaeoglobus fulgidus paralogs, respectively. The LonA subfamily is defined by the presence of a large N-terminal domain, whereas the LonB subfamily has no such domain, but has a membrane-spanning domain that anchors the protein to the cytoplasmic side of the membrane. The two subfamilies also differ in their consensus sequences. Recent crystal structures for several individual domains and sub-fragments of Lon proteases have begun to illuminate similarities and differences in structure,function relationships between the two subfamilies. Differences in orientation of the active site residues in several isolated Lon protease domains point to possible roles for the AAA+ domains and/or substrates in positioning the catalytic residues within the active site. Structures of the proteolytic domains have also indicated a possible hexameric arrangement of subunits in the native state of bacterial Lon proteases. The structure of a large segment of the N-terminal domain has revealed a folding motif present in other protein families of unknown function and should lead to new insights regarding ways in which Lon interacts with substrates or other cellular factors. These first glimpses of the structure of Lon are heralding an exciting new era of research on this ancient family of proteases. [source]