Abstract
BackgroundCell contain diverse array of proteins with different molecular weight and isoelectric point (pI). The molecular weight and pI of protein play important role in determining the molecular biochemical function. Therefore, it was important to understand the detail regarding the molecular weight and pI of the plant proteins.ResultsA proteome-wide analysis of plant proteomes from 145 species revealed a pI range of 1.99 (epsin) to 13.96 (hypothetical protein). The spectrum of molecular mass of the plant proteins varied from 0.54 to 2236.8 kDa. A putative Type-I polyketide synthase (22244 amino acids) in Volvox carteri was found to be the largest protein in the plant kingdom. However, Type-I polyketide synthase was not found in higher plant species. Titin (806.46 kDa) and misin/midasin (730.02 kDa) were the largest proteins identified in higher plant species. The pI and molecular weight of the plant proteins showed a trimodal distribution. An acidic pI (56.44% of proteins) was found to be predominant over a basic pI (43.34% of proteins) and the abundance of acidic pI proteins was higher in unicellular algae species relative to multicellular higher plants. In contrast, the seaweed, Porphyra umbilicalis, possesses a higher proportion of basic pI proteins (70.09%). Plant proteomes were also found to contain selenocysteine (Sec), amino acid that was found only in lower eukaryotic aquatic plant lineage. Amino acid composition analysis showed Leu was high and Trp was low abundant amino acids in the plant proteome. Additionally, the plant proteomes also possess ambiguous amino acids Xaa (unknown), Asx (asparagine or aspartic acid), Glx (glutamine or glutamic acid), and Xle (leucine or isoleucine) as well.ConclusionThe diverse molecular weight and isoelectric point range of plant proteome will be helpful to understand their biochemical and functional aspects. The presence of selenocysteine proteins in lower eukaryotic organism is of interest and their expression in higher plant system can help us to understand their functional role.
Highlights
Cell contain diverse array of proteins with different molecular weight and isoelectric point
Plant proteins range from 0.54 kDa to 2236.8 kDa A proteome-based analysis of plant proteins of 144 plant species that included more than 5.86 million protein sequences was considered to study the molecular mass, pI, and amino acid composition of proteins that exist in plant proteomes (Additional file 2: Table S1)
The analysis revealed that the molecular mass of plant proteomes ranged from 0.54 kDa to 2236.8 kDa
Summary
Cell contain diverse array of proteins with different molecular weight and isoelectric point (pI). The molecular weight and pI of protein play important role in determining the molecular biochemical function. It was important to understand the detail regarding the molecular weight and pI of the plant proteins. The isoelectric or isoionic point of a protein is the pH at which a protein carries no net electrical charge and is considered neutral [1,2,3,4]. The major ionisable groups present in the amino acids are arginine, aspartate, cysteine, histidine, glutamate, lysine, and glutamate, where they play a major role in determining the pI of a protein [6,7,8]. An estimated isoelectric point is highly important and a commonly identified parameter
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