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

Abstract

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 that S. pneumoniae cleaves sialic acid from human glycoconjugates to be used as a carbohydrate source. The satABC genes are required for growth and import of sialic acid. The satABC 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 identified msmK as a candidate based on similarity to other known carbohydrate ATPases. Recombinant MsmK hydrolyzed ATP, revealing that MsmK is an ATPase. An msmK 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 that msmK is also required for growth on raffinose and maltotetraose, which are the substrates of two other characterized carbohydrate ABC transporters. Furthermore, an msmK mutant was reduced in airway colonization. Together, these data imply that in vivo, MsmK energizes multiple carbohydrate transporters in S. pneumoniae. This is the first demonstration of a shared ATPase in a pathogenic bacterium.

The ABC Transporter Encoded at the Pneumococcal Fructooligosaccharide Utilization Locus Determines the Ability To Utilize Long- and Short-Chain Fructooligosaccharides

“…It had previously been suggested that import by this transporter was not energized by MsmK because an msmK mutant had no growth defect on sucrose (6,21). We believe that growth on sucrose is primarily via the PTS ScrT, which is ATPase independent, and therefore, loss of the ATPase does not affect growth under these conditions.…”

“…We also demonstrate that mutation of msmK does not further reduce the growth of the scrT mutant on GF2 (data not shown). As msmK has been demonstrated to energize all pneumococcal CUT1 family trans- porters of known function (21), these data suggest that residual transport is due to the PTS. It was previously reported that FusH (SusH) can compensate for the loss of ScrH during growth on sucrose (3).…”

“…We previously identified the ATPase MsmK, encoded by a gene at a distinct site in the genome, that is required for growth on the substrates of three characterized CUT1 ABC transporters (21). It was reported that MsmK did not contribute to pneumococcal growth on sucrose (6,21). As a result it was suggested that the ATP-binding cassette protein energizing SP_1796-98 was likely not MsmK (6).…”

“…Each of these loci lacks a gene(s) encoding the ATPase required to energize transport. We previously identified the ATPase MsmK, encoded by a gene at a distinct site in the genome, that is required for growth on the substrates of three characterized CUT1 ABC transporters (21). It was reported that MsmK did not contribute to pneumococcal growth on sucrose (6,21).…”

Structural and Functional Characterization of an Orphan ATP-Binding Cassette ATPase Involved in Manganese Utilization and Tolerance in Leptospira spp

“…Addition of 100 M MnCl 2 , a toxic concentration for L. interrogans (Fig. 2) (48)(49)(50), although to our knowledge not with both import and export systems. Alternatively, the LEPBIa2866 or LIC12079 ATPase could serve in a non-transport-related process that allows utilization of Mn 2ϩ .…”