INTRODUCTION:

Astragalus Membranaceus contains saponins, sucrose, polysaccharides, and a variety of amino acids. It is an important herb in traditional Chinese medicine. Astragalus Membranaceus in the Chinese medicine could be the most basic medicine used to improve the immune function of the lung and respiratory system, enhance spleen function and metabolic capacity, etc. meanwhile, Astragalus Membranaceus has many good effect for health, such as reducing blood viscosity, regulating blood sugar, anti-hypoxia, anti-tumor and enhancing immunity, all of these effect can be used to treat heart disease.

Plasma membrane intrinsic protein is the biofilm contained protein, exist in many plants, such as Rhododendron catawbiense, Pyrus pyrifolia, Glycyrrhiza uralensis, Hevea brasiliensis, Tamarix hispida, et al. which conduct the main responsibility of biofilm function [1-5].

Hydrophobic part of the inner plasma membrane intrinsic protein covalently bound to the phospholipid. Extrinsic plasma membrane intrinsic protein binds to the outer end of the intrinsic protein by non-covalent bonding. Plasma membrane intrinsic protein plays a variety of functions in plant. So, the Plasma membrane intrinsic protein attracts many scholars [6-10].

The function of Astragalus membranaceus in Chinese traditional medicine is considered to be an herb which could conduct as anti-free radical damage, anti-aging. Many functions of Astragalus membranaceus are explored by lots of scholars, but when its ingredient: the plasma membrane intrinsic protein is concerned; there are not many scholars committed to the issues although lots of scientist studied the related questions such as Ning Yang, et al. studied the plasma membrane protein map in rice [11], Pablo Mateos-Gil, et al. studied the super-resolution imaging of plasma membrane proteins with click chemistry [12], Ren Li, et al. tended to think that the plasma membrane intrinsic proteins may enhanced drought stress tolerance in tomato[13], and so on [14-16]. In this paper, main physical characteristic of plasma membrane intrinsic protein in Astragalus membranaceus is studied from the bioinformatics view.

MATERIALS AND METHODS:

In order to study the plasma membrane intrinsic protein in Astragalus membranaceus, the peptide protein sequences data is from NCBI (accession number: AAW80918). Composition, molecular weight, theoretical isoelectric point and other parameters of plasma membrane intrinsic protein are investigated via the protparam system [17]. The hydrophobicity of plasma membrane intrinsic protein is analyzed by the protscale system [18].

The transmembrane region of plasma membrane intrinsic protein is analyzed by using TMHMM method [19]. Signal peptide analysis was performed using SignalP system [20]. Secondary structure information of Plasma membrane intrinsic protein is analyzed via the psipred online analysis system, such as the peptide curl, and folding characteristics and so on [21]. The homology modeling study utilizes the online tools provided via Swiss-model, and the results of the system analyzed could show the 3D structural predictions [22]. Last, the phosphorylation site prediction is conducted on the online system NetPhos [23].

RESULTS AND DISCUSSION:

Physical and chemical properties for the plasma membrane intrinsic protein is studied by protparam prediction system is used for studying it. The physical and chemical properties concluding: number of amino acids is 283, molecular weight is 30244.19, total number of atoms is 4279, and instability index is 30 (see Table 1). Then, the composition of plasma membrane intrinsic protein is shown in Figure 1.

Table 1 Physical and chemical properties of plasma membrane intrinsic protein

Parameter	Perdition results
Number of amino acids	283
Molecular weight	30244.19
Theoretical pI	8.28
Formula	C₁₄₀₈H₂₁₃₉N₃₄₉O₃₇₃S₁₀
Total number of atoms	4279
Instability index	30

Figure 1. Amino acids composition of plasma membrane intrinsic protein

Hydrophobicity is an inherent characteristic of a protein molecular; it is determined by the amino acids sequences. So, the Hydrophobicity map of amino acids sequences usually is calculated to reveal the hydrophobicity of a protein. Here, hydrophobicity within plasma membrane intrinsic protein is predicted by the Hphoh./ Kyte and Doolittle scale in ExPASy's ProtScale program. The result is shown in figure 2, from the figure 2, while vertical value above 0 denotes the hydrophobic area, strong hydrophobic can be seen in plasma membrane intrinsic protein. There are more hydrophobic amino acid residues than the hydrophilic amino acid residues in the plasma membrane intrinsic protein, and the plasma membrane intrinsic protein is biased towards hydrophobic substances overall. But in the figure 2, there are also several hydrophilic areas, their hydrophilic value is lower than -2.

Figure 2. Hydrophobic characteristics of plasma membrane intrinsic protein

From the figure 2, hydrophobic and hydrophilic appear alternately in the plasma membrane intrinsic protein. Meanwhile the hydrophobic amino acids usually make up the transmembrane region. Here, TMHMM predicted system is used to confirm this phenomenon. The transmembrane region of plasma membrane intrinsic protein predicted by using the TMHMM system is as shown in Figure 3. The result shows that there are six transmembrane region in plasma membrane intrinsic protein.

Figure 3. Prediction result of transmembrane region in plasma membrane intrinsic protein

Different domain of plasma membrane intrinsic protein may interact with each other and with other proteins for its properties fall in transimodal proteins [24-25]. It is necessary to explore whether there is a signal peptide in the plasma membrane intrinsic protein. The signal peptide property of plasma membrane intrinsic protein is predicted via SignalP, and the result is shown in Figure 4, the C-score denote the signal peptide cleavage site value, S-score is the signal peptide value, Y-score is the integrated score of shear point. From the Figure 4, it is easily to find that there is no signal peptide in the plasma membrane intrinsic protein for none of the three value is higher than 0.2.

Figure 4. Signal peptide analysis of Plasma membrane intrinsic protein

The secondary structure of the protein contains the interaction between the local residues regulated by the hydrogen bond. The most common secondary structure is the α-helix, β-fold, β-angle and random curl. Random curl is not a true secondary structure, but it is a structure lack of regular rules. Most of the time, the sequence of protein is not enough to predict the secondary structure for the possibility of folding is not single, but the sequence of protein is the main factor that can determine its secondary structure. The Psipred prediction system is now used to predict the secondary structure of plasma membrane intrinsic protein. The secondary structure of plasma membrane intrinsic protein prediction result is shown in Figure 5. There are nine helixes and four strands in its secondary structure.

Figure 5. Secondary structure of Plasma membrane intrinsic protein

The famous Swiss-Model system is usually used to predict the 3D structure of a protein when the amino acid sequence is known. Here, the system is used for predicting the 3D structure of plasma membrane intrinsic protein and the result is shown in Figure 6. The plasma membrane intrinsic protein is mainly composed of α-helixes with some β-sheet areas. In Figure 6, it also can be seen that there is no signal peptide in the structure.

Figure 6. Tertiary structure of plasma membrane intrinsic protein

The main sites for protein phosphorylation are serine, threonine and tyrosine. Quantitative studies of protein phosphorylation have great importance and can benefit to the study on biological activity of proteins. The prediction of protein phosphorylation sites from the perspective of bioinformatics is also a convenient way to study the protein properties. We used the NetPhos protein phosphorylation site to predict the phosphorylation sites of the plasma membrane intrinsic protein. The results are shown in Figure 7. The number of serine phosphorylation sites is shown to be high, and there are nine high potential serine phosphorylation sites with potential value is higher than 0.9, there are two tyrosine phosphorylation sites are higher than 0.9.

Figure 7. Phosphorylation site prediction results of the plasma membrane intrinsic protein

Application of Astragalus membranaceus in traditional medicine in China has been a few thousand of years. Lots of scientists have been studied its bio-functions by from different aspect, such as its antibacterial function [26], cytotoxicity and protective effects [27], antioxidant activity[28], antitumor and immunomodulatory activity[29], et al., but the specific mechanism of medicinal ingredients of Astragalus membranaceus such as the plasma membrane intrinsic protein is still need further study especially from the perspective of bioinformatics.

CONCLUSION:

It is important to investigate information contained in herbs which used frequently in traditional Chinese medicine by these data. Although protein techniques can be used for obtaining protein expression data, the bioinformatics tools are very important for checking these things. In this study, the biological information especially its physical and chemical characters contained in plasma membrane intrinsic protein are systematically studied from its sequence, the basic physical and chemical properties of it is predicted via several famous bioinformatics tools, which provided a reference for further understanding of Astragalus membranaceus. The 3D structure of the plasma membrane intrinsic protein is predicted to in order to understand its structural characteristics and reveal further use of Astragalus membranaceus in medicine.

ACKNOWLEDGMENTS:

This research work was supported by president fund of Xi’an Technological University (No.XAGDXJJ14011).

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Received on 07.08.2017 Accepted on 18.10.2017

Asian J. Res. Pharm. Sci. 2017; 7(4):235-239.

DOI: 10.5958/2231-5659.2017.00037.6

ABSTRACT:

MATERIALS AND METHODS:

RESULTS AND DISCUSSION:

CONCLUSION:

REFERENCES: