studied G212 mutant which exhibited H
+ leakiness. However, new sequence analysis (Fig. 9) shows that the conserved residues are not universal among alkaliphiles.
These conserved residues are important only to alkaliphilic Bacillus strains and
probably to related genera. If these residues are important as they are claimed to
be, it would have been universal among alkaliphilic bacteria. But that does not seem
to be the case. Even among alkaliphilic Bacillus a-subunit, some sequences lack
conserved residues such as V177 or G212 [170]. Moreover, most of the mutational
studies made so far did not pinpoint the exact high pH adaptive role of the conserved
residues. However, the growing evidence suggests that the alkaliphilic Bacillus spp.
ATP synthase a-subunit could be involved in preventing H
+ leakage. In addition, the
results of the studies indicate a possibility that ATP synthase of alkaliphiles evolved
an efficient system of capture and translocation of H
+ to cytoplasm. However, it
needs further mutational and structural studies to establish the real high pH adaptation of these structures.
Adaptations of the c-Subunit
Amino acid sequence alignment studies on c-subunit of ATP synthase revealed the
presence of two conserved motifs, 16AxAxAVA and 51PxxExxP, in alkaliphilic
Fig. 9 Sequence alignment of the a-subunit of TMH4 and TMH5. The sequence GenBank
accession numbers are given in parentheses. The alignment includes five Gram-positive alkaliphilic
Bacillus strains – B. pseudofirmus OF4 (AAG48358), B. bogoriensis (WP_026672803.1),
B. wakoensis (WP_034748151.1), B. alkalitelluris (WP_088077058.1), and B. marmarensis
DSM 21297 (ERN51921.1). A sequence from a Gram-positive alkaliphilic anaerobe
Anaerobacillus alkalidiazotrophicus (OIJ21792.1) is also included. Six sequences are from
Gram-negative alkaliphiles – Pseudomonas alcaliphila JAB1 (APU32731.1), Alkalimonas
amylolytica (WP_091342750.1), Halomonas desiderata SP1 (OUE41273.1), Bogoriella
caseilytica (WP_123305435.1), Alkalispirillum mobile (WP_121443140.1), and Brevibacillus
laterosporus (PCN45399.1). In addition, the alignment includes a sequence from alkaliphilic
cyanobacteria Aphanothece halophytica (BAK19941.1) and two sequences of non-alkaliphilic
strains, B. subtilis 168 (NP_391568.1) and E. coli (WP_078180285.1)
108
G. Mamo
+ leakiness. However, new sequence analysis (Fig. 9) shows that the conserved residues are not universal among alkaliphiles.
These conserved residues are important only to alkaliphilic Bacillus strains and
probably to related genera. If these residues are important as they are claimed to
be, it would have been universal among alkaliphilic bacteria. But that does not seem
to be the case. Even among alkaliphilic Bacillus a-subunit, some sequences lack
conserved residues such as V177 or G212 [170]. Moreover, most of the mutational
studies made so far did not pinpoint the exact high pH adaptive role of the conserved
residues. However, the growing evidence suggests that the alkaliphilic Bacillus spp.
ATP synthase a-subunit could be involved in preventing H
+ leakage. In addition, the
results of the studies indicate a possibility that ATP synthase of alkaliphiles evolved
an efficient system of capture and translocation of H
+ to cytoplasm. However, it
needs further mutational and structural studies to establish the real high pH adaptation of these structures.
Adaptations of the c-Subunit
Amino acid sequence alignment studies on c-subunit of ATP synthase revealed the
presence of two conserved motifs, 16AxAxAVA and 51PxxExxP, in alkaliphilic
Fig. 9 Sequence alignment of the a-subunit of TMH4 and TMH5. The sequence GenBank
accession numbers are given in parentheses. The alignment includes five Gram-positive alkaliphilic
Bacillus strains – B. pseudofirmus OF4 (AAG48358), B. bogoriensis (WP_026672803.1),
B. wakoensis (WP_034748151.1), B. alkalitelluris (WP_088077058.1), and B. marmarensis
DSM 21297 (ERN51921.1). A sequence from a Gram-positive alkaliphilic anaerobe
Anaerobacillus alkalidiazotrophicus (OIJ21792.1) is also included. Six sequences are from
Gram-negative alkaliphiles – Pseudomonas alcaliphila JAB1 (APU32731.1), Alkalimonas
amylolytica (WP_091342750.1), Halomonas desiderata SP1 (OUE41273.1), Bogoriella
caseilytica (WP_123305435.1), Alkalispirillum mobile (WP_121443140.1), and Brevibacillus
laterosporus (PCN45399.1). In addition, the alignment includes a sequence from alkaliphilic
cyanobacteria Aphanothece halophytica (BAK19941.1) and two sequences of non-alkaliphilic
strains, B. subtilis 168 (NP_391568.1) and E. coli (WP_078180285.1)
108
G. Mamo