Structure of F ₁ -ATPase from the obligate anaerobe Fusobacterium nucleatum

Abstract

The crystal structure of the F 1 -catalytic domain of the adenosine triphosphate (ATP) synthase has been determined from the pathogenic anaerobic bacterium Fusobacterium nucleatum . The enzyme can hydrolyse ATP but is partially inhibited. The structure is similar to those of the F 1 -ATPases from Caldalkalibacillus thermarum , which is more strongly inhibited in ATP hydrolysis, and in Mycobacterium smegmatis , which has a very low ATP hydrolytic activity. The β E -subunits in all three enzymes are in the conventional ‘open’ state, and in the case of C. thermarum and M. smegmatis , they are occupied by an ADP and phosphate (or sulfate), but in F. nucleatum , the occupancy by ADP appears to be partial. It is likely that the hydrolytic activity of the F. nucleatum enzyme is regulated by the concentration of ADP, as in mitochondria.

F1·Fo ATP Synthase/ATPase: Contemporary View on Unidirectional Catalysis

“…The degree of ADP(Mg 2+ )-inhibition varies in different organisms; ATP hydrolysis is significantly inhibited in Bacillus subtilis [ 58 , 59 ] and very strongly inhibited in P. denitrificans [ 49 , 54 ] compared to other bacterial F 1 ·F o . The strength of inhibition correlates with the occupancy of the catalytic site by ADP(Mg 2+ ): for an enzyme with a strongly inhibited ATPase activity from Caldalkalibacillus thermarum and M. smegmatis , complete occupancy is shown, and for an enzyme with incomplete inhibition from Fusobacterium nucleatum, only partial occupancy is shown [ 3 ].…”

“…Although ATP-dependent autoinhibition of F 1 ·F o by the CTD of the ε subunit has been shown for some bacterial species [ 66 , 67 ], this regulatory mechanism likely is not conserved in other genera of bacteria [ 3 , 68 ]. Thus, the ε subunit of C. thermarum is in the “down” conformation with the ATP and Mg 2+ bound [ 67 ].…”

“…All F 1 ·F o from various sources have a common structure: they consist of two main parts, the hydrophilic F 1 and the hydrophobic F o complexes. For most organisms routinely used in research, structures of F 1 have been established, mainly by X-ray analysis [ 1 , 2 , 3 ], most detailed for mitochondrial [ 4 ] and yeast [ 1 ] F 1 ·F o and less for bacteria [ 4 ]. The hydrophobic F o structure is less susceptible to crystallization and is being studied by intensively developing electron cryomicroscopy (cryoEM) [ 5 , 6 ].…”

Regulatory Mechanisms and Environmental Adaptation of the F-ATPase Family

“…Crystal structures of purified F 1 reveal a central stalk that penetrates into the head piece, which contains the catalytic sites. [8][9][10][11][12][13][14][15] Cryo-electron microscopy (cryo-EM) analysis of the F O F 1 complex has revealed a membrane-embedded subunit assembly and a stalk connecting F 1 and F O at the periphery. [16][17][18][19][20][21][22][23][24][25][26] The F 1 has three catalytic sites with different nucleotide affinities at the three interfaces of alternately assembled α and β subunits 8) (Fig.…”

“…12,21,69) By contrast, structures of the same subunit in various bacteria, such as M. smegmatis, Caldalkalibacillus thermarum, and Fusobacterium nucleatum, show different helix structures that are folded toward the membrane side in a compact form. [13][14][15]26) A similar compact form of the ε subunit in E. coli was suggested through the structural analysis of isolated ε subunits and crosslinking experiments between the introduced Cys residues in the ε and c subunits. 64,65,70) The region was suggested to change conformations to regulate ATPase activity in E. coli and Bacillus PS3 enzymes.…”