Novel functional insights into a modified sugar-binding protein from Synechococcus MITS9220

Benjamin A. Ford, Katharine A. Michie, Ian Paulsen, Bridget C. Mabbutt, Bhumika S. Shah*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
75 Downloads (Pure)

Abstract

Paradigms of metabolic strategies employed by photoautotrophic marine picocyanobacteria have been challenged in recent years. Based on genomic annotations, picocyanobacteria are predicted to assimilate organic nutrients via ATP-binding cassette importers, a process mediated by substrate-binding proteins. We report the functional characterisation of a modified sugar-binding protein, MsBP, from a marine Synechococcus strain, MITS9220. Ligand screening of MsBP shows a specific affinity for zinc (KD ~ 1.3 μM) and a preference for phosphate-modified sugars, such as fructose-1,6-biphosphate, in the presence of zinc (KD ~ 5.8 μM). Our crystal structures of apo MsBP (no zinc or substrate-bound) and Zn-MsBP (with zinc-bound) show that the presence of zinc induces structural differences, leading to a partially-closed substrate-binding cavity. The Zn-MsBP structure also sequesters several sulphate ions from the crystallisation condition, including two in the binding cleft, appropriately placed to mimic the orientation of adducts of a biphosphate hexose. Combined with a previously unseen positively charged binding cleft in our two structures and our binding affinity data, these observations highlight novel molecular variations on the sugar-binding SBP scaffold. Our findings lend further evidence to a proposed sugar acquisition mechanism in picocyanobacteria alluding to a mixotrophic strategy within these ubiquitous photosynthetic bacteria.
Original languageEnglish
Article number4805
Pages (from-to)1-16
Number of pages16
JournalScientific Reports
Volume12
Issue number1
DOIs
Publication statusPublished - Dec 2022

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Copyright the Author(s) 2022. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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