Metallothionien (MT) is one of metal binding protein groups which has a low molecular weight, cysteine-rich in its amino acid sequence, and metal-binding properties. According to the amino acid sequence, this proteins are classified into four classes. Class 1 metallothionein comprises six Cys-another amino acid-Cys motifs which are distributed equally between two domains. Class 2 metallothionein has two cystein-rich domains separated by approximately 40 amino acid residues. In the N-terminal domain, class 3 metallothionein only contains four Cys residues which the first three consensus sequence is Cys-Gly-Asn-Cys-Asp-Cys and the fourth cysteine is contained within a highly conserved motif, Gln-Cys-Xaa-Lys-Lys-Gly. Class 4 metallothionein has three cysteine-rich domains with each domain containing 5 or 6 conserved cysteine residues and are separated by 10 to 15 residues.

 

Several types of plant especially in Poaceae family have the potency to be used in phytoremediation technique to clean up the contaminated land area. The function in absorbing the heavy metals by the accumulator plant is regulated by many genes, by which, one is Metallothionein (MT) gene. It has been reported that MT gene plays an important role in the homeostasis of essensial metals and also in the detoxification of toxic metals. Meanwhile, MT also functions as a chelator that can bind a wide range of heavy metals

 

Due to no information about the fuctional domains of MT gene  in plants, study the sequence variation of MT gene is required to find out the conserved region of this gene, especially in Poaceae family, related to MT gene function for phytoremediation. The homology of MT gene presents the information about the genetic relatedness of the gene in interspecies. It is assumed that homologous sequences have the similar structures and similar functions. In this study, the MT gene sequences in Poaceae plants, such as Hordeum vulgare, Sorghum bicolor, and Setaria itálica were obtained from the genetic sequence database operated by NCBI (National Center for Biotechnology Information). T-cofee tool was used to align the sequences therefore it identified the similarity región between the sequence. BLAST (Basic Local Alignment Search Tool) was used to compare the sequence database and calculate the significant of matches. The results indicated that MT gene sequence in between Poaceae plants showed a high homology in several regions. The interesting thing was MT sequence of Chloris virgata had the sequence identity around 92% with MT sequence of Allium sativum which was grouped in Alliaceae family. By knowing the sequence variations, it can lead to the potential future research for discovering the functional domains of MT gene particularly in the metal absorber plants.