The Molecular Mass and Isoelectric Point of Plant Proteomes

Abstract

Background 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. Therefore, it was important to understand the detail regarding the molecular weight and pI of the plant proteins. Results A 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. Conclusion The 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.

Construction of Anti-codon Table of the Plant Kingdom and Evolution of tRNA Selenocysteine (tRNASec)

“…The study also reveals that plant genomes encode tRNA Leu , tRNA Ser , and tRNA Arg more frequently than other tRNAs. A proteome-wide analysis by Mohanta et al, (2019) reported a higher abundance of Leu amino acids in the proteomes of the Plant Kingdom [65]. This observation directly corroborates that the number and abundance of tRNA Leu genes in genome is directly proportional to the number of Leu amino acids in the proteome.…”

A Critical Review of Bottom-Up Proteomics: The Good, the Bad, and the Future of This Field

“…The term proteome refers to all proteins that are produced or modified by an organism (e.g., human [ 1 ], animal [ 2 ], plant [ 3 ], bacteria [ 4 ]) or living system (e.g., organ, cell culture, complex community from an environmental sample)). The term “proteome” and the first dedicated proteomics laboratory were introduced in 1994 by Wilkins et al to describe proteins as a complement to genomic data [ 5 ].…”

Construction of Anti-codon Table of the Plant Kingdom and Evolution of tRNA Selenocysteine (tRNAsec)

“…The study also reveals that plant genomes encode tRNA Leu , tRNA Ser , and tRNA Arg more frequently than other tRNAs. A proteome-wide analysis by Mohanta et al, (2019) reported a higher abundance of Leu amino acids in the proteomes of the Plant Kingdom [62]. This observation directly corroborates that the number and abundance of tRNA Leu genes in genome is directly proportional to the number of Leu amino acids in the proteome.…”