Evolution and isoforms of V-ATPase subunits

Abstract

The structure of V- and F-ATPases/ATP synthases is remarkably conserved throughout evolution. Sequence analyses show that the V- and F-ATPases evolved from the same enzyme that was already present in the last common ancestor of all known extant life forms. The catalytic and non-catalytic subunits found in the dissociable head groups of both V-ATPases and F-ATPases are paralogous subunits, i.e. these two types of subunits evolved from a common ancestral gene. The gene duplication giving rise to these two genes (i.e. those encoding the catalytic and non-catalytic subunits) pre-dates the time of the last common ancestor. Similarities between the V- and F-ATPase subunits and an ATPase-like protein that is implicated in flagellar assembly are evaluated with regard to the early evolution of ATPases. Mapping of gene duplication events that occurred in the evolution of the proteolipid, the non-catalytic and the catalytic subunits onto the tree of life leads to a prediction of the likely quaternary structure of the encoded ATPases. The phylogenetic implications of V-ATPases found in eubacteria are discussed. Different V-ATPase isoforms have been detected in some higher eukaryotes, whereas others were shown to have only a single gene encoding the catalytic V-ATPase subunit. These data are analyzed with respect to the possible function of the different isoforms (tissue-specific, organelle-specific). The point in evolution at which the different isoforms arose is mapped by phylogenetic analysis.

The Plant V-ATPase

“…Besides environmental influences, some isoforms show organ-specificity like VHA-E2 and VHA-G3, which are expressed in pollen, but most show stress-responsive expression patterns ( Hanitzsch et al, 2007 ). In contrast to A. thaliana where VHA-A is encoded by a single gene and therefore vulnerable to mutations, it is encoded by at least two genes in rice, tomato, and carrot, which are organ-specific expressed ( Gogarten et al, 1992 ; Bageshwar et al, 2005 ; Hanitzsch et al, 2007 ). At the level of the V 0 sector, all five VHA-c isogenes were expressed in leaves, and the same was observed for VHA-c”1, while the transcript of VHA-c3 was additionally high in root caps of seedlings and the expression of VHA-c”2 was not detectable ( Padmanaban et al, 2004 ; Hanitzsch et al, 2007 ; Seidel et al, 2008 ).…”