Role of a Conserved Prolyl Residue (Pro173) of MotA in the Mechanochemical Reaction Cycle of the Proton-Driven Flagellar Motor of Salmonella

Assembly and Activation of the MotA/B Proton Channel Complex of the Proton-Driven Flagellar Motor of Salmonella enterica

“…However, the P173A mutation causes a sharp decline in the torque-speed curve with a maximum rotation rate of ca. 25 Hz (Nakamura et al, 2009b). These suggest that the P173A mutation reduces the maximum proton conductivity of the MotA/B complex but not the efficiency of energy coupling between proton translocation and torque generation.…”

“…Two conserved charged residues, Arg-90 and Glu-98, in the cytoplasmic loop between TM2 and TM3 are involved in electrostatic interactions with charged residues in the C-terminal domain of FliG to produce torque (Zhou and Blair, 1997;Zhou et al, 1998a). A conserved proline residue of MotA, Pro-173 and Pro-222, are thought to be involved in conformational changes of the stator complex that couple proton influx with torque generation (Braun et al, 1999;Nakamura et al, 2009b). The absolutely conserved and functionally critical aspartic acid residue, Asp-33 of MotB is Rotation rate (Hz) Rotation rate (Hz) located near the cytoplasmic end of its TM and is postulated to be a proton-binding site (Sharp et al, 1995;Togashi et al, 1997;Zhou et al, 1998b;Che et al, 2008;Morimoto et al, 2010a).…”

“…This suggests that Pro-173 of MotA is positioned in the proton channel near Asp-32 of MotB, which corresponds to Asp-33 in Salmonella MotB (Braun et al, 2004). The Salmonella motA(P173A) mutant produces stall torque at wild-type levels (Nakamura et al, 2009b). However, the P173A mutation causes a sharp decline in the torque-speed curve with a maximum rotation rate of ca.…”

“…Since Pro-173 of MotA is likely to be very close to Asp-33 of MotB in the MotA/B complex structure (Braun et al, 2004), and because Pro is known to induce a kink in -helix, its replacement with Ala would relax the conformational strain of the MotA/B complex, resulting in a change in protein dynamics to slow down the rates of conformational changes that switch the exposure of Asp-33 to the outside or the inside of the cell. Therefore, Pro-173 is proposed to play an important role in facilitating the resetting of the position of Asp-33 relative to the proton pathway in the conformational change between the two distinct states to facilitate proton translocation when the motor spins at high speed (Nakamura et al, 2009b).…”

Bioinformatic analysis of the flagellar system of the rickettsia-like alphaproteobacteria Candidatus Hepatobacter penaei

“…La Val35 de MotA interactúa con el Asp33 de MotB para la formación del canal hidrofóbico por el cual se da el flujo de protones (Braun et al 2004). De igual manera, la Pro173 de MotA, tiene la función de anclaje con Asp33 de MotB asegurando de esta manera el funcionamiento del motor del sistema flagelar (Nakamura et al 2009). La presencia de ambos aminoácidos en la secuencia deducida corresponde a MotA apoya la idea que el gen codificante para la proteína MotB se encuentre en el genoma de Candidatus Hepatobacter penaei, aunque en este estudio no se logró identificar.…”