Stimulation of the Maltose Transporter ATPase by Unliganded Maltose Binding Protein

Journal Article · Mon Feb 15 04:00:00 EST 2010 · Biochemistry-US

DOI:https://doi.org/10.1021/bi9007066· OSTI ID:1006105

Gould, Alister D; Telmer, Patrick G; Shilton, Brian H

ATP hydrolysis by the maltose transporter (MalFGK{sub 2}) is regulated by maltose binding protein (MBP). Binding of maltose to MBP brings about a conformational change from open to closed that leads to a strong stimulation of the MalFGK{sub 2} ATPase. In this study, we address the long-standing but enigmatic observation that unliganded MBP is also able to stimulate MalFGK{sub 2}. Although the mechanism of this stimulation is not understood, it is sometimes attributed to a small amount of closed (but unliganded) MBP that may exist in solution. To gain insight into how MBP regulates the MalFGK{sub 2} ATPase, we have investigated whether the open or the closed conformation of MBP is responsible for MalFGK{sub 2} stimulation in the absence of maltose. The effect of MBP concentration on the stimulation of MalFGK{sub 2} was assessed: for unliganded MBP, the apparent K{sub M} for stimulation of MalFGK{sub 2} was below 1 {micro}M, while for maltose-bound MBP, the K{sub M} was approximately 15 {micro}M. We show that engineered MBP molecules in which the open-closed equilibrium has been shifted toward the closed conformation have a decreased ability to stimulate MalFGK{sub 2}. These results indicate that stimulation of the MalFGK{sub 2} ATPase by unliganded MBP does not proceed through a closed conformation and instead must operate through a different mechanism than stimulation by liganded MBP. One possible explanation is that the open conformation is able to activate the MalFGK{sub 2} ATPase directly.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE
• OSTI ID: 1006105
• Journal Information: Biochemistry-US, Journal Name: Biochemistry-US Journal Issue: (33) ; 08, 2009 Vol. 48; ISSN 0006-2960; ISSN BICHAW
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
CONFORMATIONAL CHANGES
HYDROLYSIS
MALTOSE
PROTEINS
STIMULATION