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Publication Abstract from PubMedEscherichia coli HisJ is a type II periplasmic binding protein (PBP) that functions to reversibly capture histidine and transfer it to its cognate inner membrane ABC permease. Here we used NMR spectroscopy to determine the structure of apo-HisJ (26.5 kDa) in solution. HisJ is a bilobal protein of which the domain 1 (D1) is made up of two non-contiguous subdomains and domain 2 (D2) is expressed as the inner domain. To better understand the roles of D1 and D2 we have isolated and characterized each domain separately. Structurally, D1 closely resembles its homologous domain in apo- and holo-HisJ, while D2 is more similar to the holo-form. NMR relaxation experiments reveal that HisJ becomes more ordered upon ligand binding, while isolated D2 experiences a significant reduction in slower (ms-mus) motions compared with the homologous domain in apo-HisJ. NMR titrations reveal that D1 is able to bind histidine in a similar manner as full-length HisJ, albeit with lower affinity. Unexpectedly, isolated D1 and D2 do not interact in the presence or absence of histidine, which indicates the importance of intact interdomain connecting elements (i.e. hinge regions) for HisJ functioning. Our results shed light on the binding mechanism of type II PBPs where ligand is initially bound by D1 and D2 plays a supporting role in this dynamic process. The Role of the Two Structural Domains from the Periplasmic E. coli Histidine Binding Protein HisJ.,Chu BC, Dewolf T, Vogel HJ J Biol Chem. 2013 Sep 13. PMID:24036119[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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