@article{mbs:/content/journal/micro/10.1099/00221287-148-11-3531, author = "Nanavati, Dhaval and Noll, Kenneth M. and Romano, Antonio H.", title = "Periplasmic maltose- and glucose-binding protein activities in cell-free extracts of Thermotoga maritima", journal= "Microbiology", year = "2002", volume = "148", number = "11", pages = "3531-3537", doi = "https://doi.org/10.1099/00221287-148-11-3531", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-148-11-3531", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "ABC transporters", keywords = "sugar transport", keywords = "hyperthermophile", keywords = "transporter evolution", keywords = "ABC, ATP-binding cassette", abstract = "In this study, high-affinity maltose- and glucose-binding activities in cell-free extracts of Thermotoga maritima were detected; these activities were distinct and specific. At the gross level, the expression of binding-protein activities was repressed by growth of T. maritima in the presence of the cognate sugar. Growth of the organism in the presence of maltose reduced maltose-binding activity but not glucose-binding activity, while growth in the presence of glucose reduced glucose-binding activity but not maltose-binding activity. In competition assays, these binding activities showed distinct patterns of substrate specificity: whereas the maltose-binding activity showed specificity for α-linked glucosides, the glucose-binding activity showed a broader specificity. All maltose- and glucose-binding activity was found in the supernatant retrieved following centrifugation (100000  g ) of the cell-free extracts prepared by French-pressure-cell treatment; no activity was found in an octyl-glucoside-treated extract of the membrane fraction. The maltose-binding-protein activity was recovered from the periplasmic fraction by selective release of the periplasmic contents of T. maritima cells using a newly developed freeze–thaw procedure. Annotation of the complete genome sequence of T. maritima suggests that there may be at least two maltose-binding proteins, MalE1 and MalE2, encoded in the genome. The maltose-binding activity corresponded to a protein of 43 kDa, which was consistent in size with either of the putative proteins. These data demonstrate that the hyperthermophilic bacterium T. maritima possesses separate maltose- and glucose-binding-protein activities that are freely soluble in its periplasm, in contrast to the membrane-bound sugar-binding proteins found in archaeal hyperthermophiles.", }