Glucose Transport in the Extremely Thermoacidophilic Sulfolobus solfataricus Involves a High-Affinity Membrane-Integrated Binding Protein

Abstract

The archaeon Sulfolobus solfataricus grows optimally at 80°C and pH 2.5 to 3.5 on carbon sources such as yeast extracts, tryptone, and various sugars. Cells rapidly accumulate glucose. This transport activity involves a membrane-bound glucose-binding protein that interacts with its substrate with very high affinity (Kd of 0.43 μM) and retains high glucose affinity at very low pH values (as low as pH 0.6). The binding protein was extracted with detergent and purified to homogeneity as a 65-kDa glycoprotein. The gene coding for the binding protein was identified in the S. solfataricus P2 genome by means of the amino-terminal amino acid sequence of the purified protein. Sequence analysis suggests that the protein is anchored to the membrane via an amino-terminal transmembrane segment. Neighboring genes encode two membrane proteins and an ATP-binding subunit that are transcribed in the reverse direction, whereas a homologous gene cluster inPyrococcus horikoshii OT3 was found to be organized in an operon. These data indicate that S. solfataricus utilizes a binding-protein-dependent ATP-binding cassette transporter for the uptake of glucose.

Sugar transport in Sulfolobus solfataricus is mediated by two families of binding protein‐dependent ABC transporters

“…2C) was reciprocally inhibited by the unlabelled sugars indicating that these substrates share a common binding protein. The inhibition studies also confirmed our earlier report (Albers et al, 1999a) showing that glucose ( Fig. 2D) and galactose ( Fig.…”

“…Recently, we reported the identification of a membrane-bound binding protein that functions as a subunit of an ABC-type transport system for glucose, galactose and mannose (Albers et al, 1999a). During the purification of this protein, concanavalin A (ConA) affinity chromatography of detergent-solubilized membranes was used to purify glycosylated membrane proteins selectively (Albers et al, 1999a). As this method allows the purification of a limited number of proteins within the molecular mass range of 30±300 kDa (Fig.…”

“…3D) in the various fractions. This protein is identical to GlcS that was purified to homogeneity (Albers et al, 1999a). Like GlcS, the trehalose-binding protein is also expressed under all growth conditions (Fig.…”

ABC transporters: one, two or four extracytoplasmic substrate‐binding sites?

“…These SBPs, which are the main determinants of SBP-dependent ABC transporter specificity, were first identified in Gram-negative bacteria, where they reside in the periplasmic space (Neu and Heppel, 1965). Grampositive bacteria and Archaea, organisms without a periplasm, anchor the proteins to the outer surface of the cell membrane via an N-terminal lipid moiety ( Figure 1A) (Gilson et al, 1988;Sutcliffe and Russell, 1995) or, in the case of Archaea, use an N-terminal transmembrane segment to anchor the protein to the cytoplasmic membrane (Albers et al, 1999). The majority of SBPs involved in ABC transport consist of two domains (C-and N-lobes) that are connected by a flexible hinge (Quiocho and Ledvina, 1996;Lanfermeijer et al, 2000).…”

ABCdb: an online resource for ABC transporter repertories from sequenced archaeal and bacterial genomes

“…In gram-positive bacteria, it is either anchored to the outside of the cell via N-terminal lipid groups (Perego et al, 1991), or, in a few cases, fused to the transporter itself (van der Heide & Poolman, 2002). In archaea, it is anchored to the cytoplasmic membrane via an N-terminal transmembrane segment (Albers et al, 1999). The SBPs may have two distinct but related functions.…”