Potential involvement of N-terminal acetylation in the quantitative regulation of the epsilon subunit of chloroplast ATP synthase under drought stress.
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In plants, modulation of photosynthetic energy conversion in varying environments is often accompanied by adjustment of the abundance of photosynthetic components. In wild watermelon (Citrullus lanatus L.), proteome analysis revealed that the epsilon subunit of chloroplast ATP synthase occurs as two distinct isoforms with largely-different isoelectric points, although encoded by a single gene. Mass spectrometry (MS) analysis of the epsilon isoforms indicated that the structural difference between the epsilon isoforms lies in the presence or absence of an acetyl group at the N-terminus. The protein level of the non-acetylated epsilon isoform preferentially decreased in drought, whereas the abundance of the acetylated epsilon isoform was unchanged. Moreover, metalloprotease activity that decomposed the epsilon subunit was detected in a leaf extract from drought-stressed plants. Furthermore, in vitro assay suggested that the non-acetylated epsilon subunit was more susceptible to degradation by metalloaminopeptidase. We propose a model in which quantitative regulation of the epsilon subunit involves N-terminal acetylation and stress-induced proteases. (+info)
The plastid genome of mycoheterotrophic monocot Petrosavia stellaris exhibits both gene losses and multiple rearrangements.
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