Streptococcal solute-binding proteins (SBPs) associated with ATP-binding cassette transporters gained widespread attention first as ostensible adhesins, next as virulence determinants, and finally as metal ion transporters. In this mini-review, we will examine our current understanding of the cellular roles of these proteins, their contribution to metal ion homeostasis, and their crucial involvement in mediating streptococcal virulence. There are now more than 35 studies that have collected structural, biochemical and/or physiological data on the functions of SBPs across a broad range of bacteria. This offers a wealth of data to clarify the formerly puzzling and contentious findings regarding the metal specificity amongst this group of essential bacterial transporters. In particular we will focus on recent findings related to biological roles for manganese in streptococci. These advances will inform efforts aimed at exploiting the importance of manganese and manganese acquisition for the design of new approaches to combat serious streptococcal diseases.
KeywordsABC transporter Manganese Zinc Cluster A–I SBP Metal binding Solute-binding protein Streptococcus Virulence
This work was supported by the Australian Research Council Grant DP120103957 to C.A.M., the National Health & Medical Research Council Project Grant 1022240 and 1080784 to C.A.M., and National Institutes of Health Grants R01AI47841 and R56AI085195 to T.K. This work is solely the responsibility of the authors and does not reflect the views of the National Institutes of Health.
Conflict of interest
The authors declare no competing financial interests.
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