A Lon-Like Protease with No ATP-Powered Unfolding Activity
Resource
PLOS ONE, 7(7), e40226
Journal
PLoS ONE
Pages
e40226
Date Issued
2012
Date
2012
Author(s)
Liao, Jiahn-Haur
Kuo, Chiao-I
Huang, Ya-Yi
Lin, Yu-Ching
Lin, Yen-Chen
Yang, Chen-Yui
Wu, Wan-Ling
Chang, Wei-Hau
Liaw, Yen-Chywan
Lin, Li-Hua
Chang, Chung-I
Wu, Shih-Hsiung
Uversky, Vladimir N.
Abstract
Lon proteases are a family of ATP-dependent proteases involved in protein quality control, with a unique proteolytic domain and an AAA+ (ATPases associated with various cellular activities) module accommodated within a single polypeptide chain. They were classified into two types as either the ubiquitous soluble LonA or membrane-inserted archaeal LonB. In addition to the energy-dependent forms, a number of medically and ecologically important groups of bacteria encode a third type of Lon-like proteins in which the conserved proteolytic domain is fused to a large N-terminal fragment lacking canonical AAA+ motifs. Here we showed that these Lon-like proteases formed a clade distinct from LonA and LonB. Characterization of one such Lon-like protease from Meiothermus taiwanensis indicated that it formed a hexameric assembly with a hollow chamber similar to LonA/B. The enzyme was devoid of ATPase activity but retained an ability to bind symmetrically six nucleotides per hexamer; accordingly, structure-based alignment suggested possible existence of a non-functional AAA-like domain. The enzyme degraded unstructured or unfolded protein and peptide substrates, but not well-folded proteins, in ATP-independent manner. These results highlight a new type of Lon proteases that may be involved in breakdown of excessive damage or unfolded proteins during stress conditions without consumption of energy. © 2012 Liao et al.
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