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The beta‐clam domain of the AAA protein family AMA has energy‐independent chaperone activity and mediates hexamerization
Author(s) -
Djuranovic Sergej,
Zeth Kornelius,
Martin Jörg,
Lupas Andrei
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a488-c
Subject(s) - chaperone (clinical) , aaa proteins , biology , protein domain , c terminus , thermoplasma acidophilum , microbiology and biotechnology , biochemistry , atpase , cyclic nucleotide binding domain , chemistry , peptide sequence , gene , amino acid , enzyme , medicine , pathology
Phylogenetic analysis of the AAA family of proteins revealed a new subgroup which we named AMA‐proteins ( A rchaeglobus‐ M ethanogenic A TPase). We found by bioinformatical analysis that the N‐terminal domain of AMA proteins could assume a CDC48 domain 2‐like fold, a six stranded clam‐like structure. It was shown that domains like this in combination with another domain (double‐Ø barrel) have a role in binding protein substrates. AMA proteins consist only of a clam‐like domain and an ATPase domain. We have used heat and chemical aggregation assays of different protein substrates to assay AMA protein and parts of it for chaperone activity. We also assayed the homologous beta‐clam like domain from VAT protein (Cdc48/p97 homologue from Thermoplasma acidophilum) and we found differences in activity and oligomerization state of these domains. We have mapped sequence differences between these homologues to the loop region between two structural elements and constructed a serial of chimera loop proteins. We have also made mutations in the N‐terminal domain of AMA protein in the depicted loop region. All constructs were assayed for possible chaperone activity and oligomerization state. The results of our study show that substrate binding function and chaperone activity of AMA proteins resides in the N‐terminal domain of those proteins. We were able to show the importance of oligomerization for activity of these domains and that oligomerization is mediated by a loop region. The N‐terminal domain of AMA mediates hexamerization of full protein independently from the AAA part of protein and ATP utilization, which was not shown to be case in other AAA proteins.