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E. coli aconitase B structure reveals a HEAT-like domain with implications for protein-protein recognition
Colin H Williams1, Timothy J Stillman, Vladimir V Barynin
1Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Abstract:
The major bifunctional aconitase of Escherichia coli (AcnB) serves as either an enzymic catalyst or a mRNA-binding post-transcriptional regulator, depending on the status of its iron sulfur cluster. AcnB represents a large, distinct group of Gram-negative bacterial aconitases that have an altered domain organization relative to mitochondrial aconitase and other aconitases. Here the 2.4 A structure of E. coli AcnB reveals a high degree of conservation at the active site despite its domain reorganization. It also reveals that the additional domain, characteristic of the AcnB subfamily, is a HEAT-like domain, implying a role in protein protein recognition. This domain packs against the remainder of the protein to form a tunnel leading to the aconitase active site, potentially for substrate channeling.