Document Detail

Signal transduction and phosphoryl transfer by a FixL hybrid kinase with low oxygen affinity: importance of vicinal PAS domain and receiver aspartate.
MedLine Citation:
PMID:  23282139     Owner:  NLM     Status:  Publisher    
FixL is a prototype for heme-based sensors: multi-domain proteins that typically couple a histidine protein kinase activity to a heme-binding domain for sensing of diatomic gases such as oxygen, carbon monoxide and nitric oxide. Despite a relatively well-advanced knowledge of FixL, the importance of some of its domains has been unclear. To explore the impact of domain-domain interactions on oxygen sensing and signal transduction, we characterized and investigated the Rhizobium etli hybrid sensor ReFixL. In ReFixL, the core heme-containing PAS domain plus kinase region is preceded by a N-terminal PAS domain of unknown function and followed by a C-terminal receiver domain. The latter resembles a target substrate domain that usually occurs independently of the kinase and contains a phosphorylatable aspartate residue. We isolated the full-length ReFixL as a soluble holoprotein with a single heme-b cofactor. Despite a low affinity for oxygen (Kd O2 = 738 μM), the kinase activity was completely switched off by O2 at concentrations well below the Kd. A deletion of the first PAS domain strongly increased the oxygen affinity but essentially forbade autophosphorylation, although the truncated protein was competent to accept phosphoryl groups in trans. These studies give new insights into histidyl-aspartyl phosphoryl transfers in two-component systems and suggest that the control of ligand affinity and signal transduction by PAS domains can be direct or indirect.
Eduardo H S Sousa; Jason R Tuckerman; Ana Claudia Silva Gondim; Gonzalo Gonzalez; Marie-Alda Gilles-Gonzalez
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-2
Journal Detail:
Title:  Biochemistry     Volume:  -     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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