A Lon-like protease with no ATP-powered unfolding activity.
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.
Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
Jiahn-Haur
JH
Liao
Chiao-I
CI
Kuo
Ya-Yi
YY
Huang
Yu-Ching
YC
Lin
Yen-Chen
YC
Lin
Chen-Yui
CY
Yang
Wan-Ling
WL
Wu
Wei-Hau
WH
Chang
Yen-Chywan
YC
Liaw
Li-Hua
LH
Lin
Chung-I
CI
Chang
Shih-Hsiung
SH
Wu
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D034301:Deinococcus / Q000201:enzymology; D004789:Enzyme Activation; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D049070:Protease La / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D058767:Protein Unfolding; D016415:Sequence Alignment
D009711:Nucleotides; D049070:Protease La; D000251:Adenosine Triphosphatases; D008274:Magnesium