Identification of an ATPase, MsmK, Which Energizes Multiple Carbohydrate ABC Transporters in Streptococcus pneumoniae

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and results in over 1 million deaths each year worldwide. Asymptomatic colonization of the airway precedes disease, and acquisition of carbohydrates from the host environment is necessary for bacterial survival. We previously demonstrated thatS. pneumoniae cleaves sialic acid from human glycoconjugates to be used as a carbohydrate source. ThesatABC genes are required for growth and import of sialic acid. ThesatABC genes are predicted to encode components of an ABC transporter but not the ATPases essential to energize transport. As this subunit is essential, an ATPase must be encoded elsewhere in the genome. We identifiedmsmK as a candidate based on similarity to other known carbohydrate ATPases. Recombinant MsmK hydrolyzed ATP, revealing that MsmK is an ATPase. AnmsmK mutant was reduced in growth on and transport of sialic acid, demonstrating that MsmK is the ATPase energizing the sialic acid transporter. In addition to satABC ,S. pneumoniae contains five other loci that are predicted to encode CUT1 family carbohydrate ABC transporter components; each of these lacks a predicted ATPase. Data indicate thatmsmK is also required for growth on raffinose and maltotetraose, which are the substrates of two other characterized carbohydrate ABC transporters. Furthermore, anmsmK mutant was reduced in airway colonization. Together, these data imply thatin vivo , MsmK energizes multiple carbohydrate transporters inS. pneumoniae . This is the first demonstration of a shared ATPase in a pathogenic bacterium.