High impact information on PMA2

• The PMA2 (plasma membrane H(+)-ATPase) isoform from Nicotiana plumbaginifolia was previously shown to be capable of functionally replacing the yeast H(+)-ATPase, provided that the external pH was kept above pH 5 [1].
• 5. In this study, we used a positive selection to isolate 19 single point mutations of PMA2 which permit the growth of yeast cells at pH 4 [1].
• Finally, by complementing yeast that lacks its endogenous H(+)-ATPase with wild-type and mutant forms of the Nicotiana plumbaginifolia H(+)-ATPase isoform PMA2, we provide physiological evidence for the importance of the phosphothreonine motif in 14-3-3 binding and, hence, in the activation of the H(+)-ATPase in vivo [2].
• Moreover, the introduction of seven closely spaced mismatches near the end of a PMA1 segment with an otherwise-high level of identity with PMA2 led to a significantly increased concentration of the junctions near this end [3].
• Chimeric PMA1::PMA2 sequences, placed under the control of the PMA1 promoter, were constructed by in vivo recombination between a gapped linearized plasmid containing the PMA2 gene and four different fragments of the PMA1 gene [3].

Biological context of PMA2

• The extensive amino acid sequence homology with the fungal H+-ATPases described so far indicates that the PMA2-encoded protein is also able to function as a H+ pump [4].
• Slower development of diploids is also observed on normal minimal medium after bilateral disruption of PMA2 in the two parents [4].
• Correct in-frame assembly of the PMA sequences was screened by the expression of the lacZ reporter gene fused to the PMA2 coding region [3].
• This partially active gene differs from a wild-type revertant only by the presence of two PMA2-encoded amino acid substitutions [5].
• Revertants that can grow at pH 3.0 and on ammonium-containing plates frequently arise by ectopic recombination between pma1-105 and PMA2, a diverged gene that shares 85% DNA sequence identity with PMA1 [5].

Anatomical context of PMA2

• Activity of plasma membrane H+-ATPase and expression of PMA1 and PMA2 genes in Saccharomyces cerevisiae cells grown at optimal and low pH [6].
• Immunoelectron microscopy reveals a dramatic proliferation of intracellular structures (probably endoplasmic reticulum) in which overexpressed PMA2 protein accumulates [7].
• When PMA2 bearing a 6-His tag was expressed under a strong transcription promoter in Nicotiana tabacum BY2 cells, solubilized from microsomal membranes and purified, the penultimate threonine was found to be phosphorylated, thus validating the model [8].

Associations of PMA2 with chemical compounds

• More striking, the glucose-activated PMA2 enzyme displays a three to four times higher apparent affinity for MgATP, and maximal activity is reached with a 10-fold lower free Mg2+ concentration [9].
• Most of the suppressors either replaced the primary site mutation with alanine or restored the wild type residue by ectopic recombination with PMA2, both of which restore alpha-helical tendency [10].
• These mutations were also introduced in an activated PMA2 mutant (Gln-14 --> Asp) characterized by a higher H(+) pumping activity [11].
• Mutation of Thr-955 to alanine, aspartate, or a stop codon prevented PMA2 from complementing the yeast H(+)-ATPase [11].
• In diauxic growth, during transition to stationary phase after ethanol depletion, a further strong activation (eight-fold) of PMA2 gene transcription was observed [12].

Regulatory relationships of PMA2

• These results indicate that the PMA2 gene encodes a functional plasma membrane H(+)-ATPase and suggest a specific control of the intracellular traffic of plasma membrane ATPase [7].

Other interactions of PMA2

• The gene called PMA2 encodes a polypeptide of Mr = 102,157, which, with the exception of the 144 amino-terminal residues, is highly homologous to the structural gene PMA1 for the H+-ATPase [4].
• Unexpectedly, a fraction of the purified tagged PMA2 associated with the two yeast 14-3-3 regulatory proteins, BMH1 and BMH2 [11].

Analytical, diagnostic and therapeutic context of PMA2

• The analysis of the PMA1 and PMA2 sequence alignment, compared with reported PMA1 mutations, points to a few residue substitutions as putative contributors to the observed kinetic changes [9].
• The expression of the PMA1 and PMA2 genes during Saccharomyces cerevisiae growth in medium with glucose plus increasing concentrations of ethanol was monitored by using PMA1-lacZ and PMA2-lacZ fusions and Northern blot hybridizations of total RNA probed with PMA1 gene [13].

References