Fungal immunomodulatory proteins 3 Amino-acid Composition and Structural Characteristic of FIPs: on FIP-gts,there are two a-helices,seven B-sheets,and one The amino acid composition and structure of protein and B-turn in the predicted secondary structure (Lin et al.,1997). its function is closely related to each other.Different spatial The basic structure is crucial to forming homodimer, structure of proteins resulted in different physical properties, recognizing cell surface,and playing a role in immune chemical properties and physiological functions.Seven FIP regulation,and is necessary for the immunomodulatory genes have been isolated from various mushrooms respectively. function of FIPs.Lin et al.has analyzed the N-terminal The corresponding seven proteins encoded by these genes are sequence of FIP-gts via yeast two-hybrid and site-directed known as LZ-8(FIP-glu),FIP-gts,FIP-fve,FIP-vvo,FIP-gja, mutagenesis techniques (Lin et al.,1997). FIP-gmi and FIP-gsi (Zhou et al.,2009;Li et al.,2011). 1.7A structure of FIP-fve,studied by Paaventhan et al,showed Among the seven FIPs,only four FIPs,LZ-8(FIP-glu),FIP- that the dimmer formation was stabilized predominantly by gts,FIP-fve,and FIP-vvo,are isolated directly from the fruit- hydrophobic interactions among the N-terminal helices(Figure bodies or mycelia of natural mushrooms.Their basic 3),and was presumed to play a role in the immune function.Each characteristics are summarized in Table 1.The others are monomer consists of an N-terminal a-helix,followed by a obtained by means of the recombinant DNA technology based fibronectin III(FNIID)fold,which is a transition formation between on their homologous gene sequences.The primary structures seven B-stranded s-types and eight B-stranded h-type topologies of FIPs have high homology after aligning of amino acid (Paaventhan et al.,2003).Lacking of cysteine,FIPs may depend sequences,generally up to 60-70%(Figure 2). on other forces such as hydrophobic forces between B-sheets to maintain the appropriate conformation.At the same FIGURE 2.The blast result of FIPs Amino acid sequences time,the structure of FIPs is highly similar with the 60 immunoglobulin heavy chain variable region FIP-glu (1)MS-D-TAL IFRLAWDVKKLSFDYTPNWGRGNPNNFIDTVTFPKVLTDKAYTYRVAVSGRN (IgV)containing the complementary sites of FIP-gsi (1)MS-D-TALIFRLAWDVKKLSFDYTPTWGRGNPSRFVDNVTFPQVLADKAYTYRVVVSGRD antigen (complementarity determining domain) FIP-fve (1)MS--ATSLTFQLAYLVKKIDFDYTPNWGRGTPSSY IDNLTFPKVLTDKKYSYRVVVNGSD and composing antibody-antigen binding site with FIP-vvo (1)MSTDLTOLLFFIAYNLOKVNFDYTPOWORGNPSSYIDAVVFPRVLTNKAYOYRVVTGDKD the light chain variable region,which could be Consensus (1)MS D TALIFRLAWDVKKLSFDYTPNWGRGNPSSFIDNVTFPKVLTDKAYTYRVVVSGRD 61 specifically bound to antigen and then trigger 116 FIP-glu (59)LGVKPSYAVESDGSOKVNFLEYNSGYGIADTNT IQVFVVDPDT-N-NDFI IAQWN- immune response.Therefore,the similarities and FIP-gsi (59)LGVRPSYAVGSDGSOKVNFLEYNOGYGIADTNTIQVFVIDPDTG-ADFIIAQWN- differences between the structures of FIPs and IgV FIP-fve (59)LGVESNFAVTPSGGOT INFLOYNKGYGVADTKTIQVFVVIPDTGNSEEYIIAEWKK will be helpful to further explore on the classification FIP-vvo (61)LGIKPSYSVQADGSOKVNLLEYNGGYGVADTTTIKIYVVDPSNG-NOYLIAQWK- and identification of FIPs as well as the mechanism Consensus (61)LGVKPSYAV SDGSOKVNFLEYN GYGIADTNTIQVFVVDPDTGN NDFI IAOWN of immune regulation. TABLE 1.Basic characteristics of natural FIPs FIGURE 3.The dimmer structure of FIP-fve. Name Molecular Number of Mushroom Reference Weight(KD) Amino Acid LZ-8 (FIP-glu) 13.100 110 G.lucidum (Kino et al.,1989) FIP-gts 13.000 110 G.tsugae (Lin et al.,1997) FIP-fve 12.704 114 F velutipes (Ko et al.,1995) FIP-vvo 12.667 112 V.volvacea (Hsu et al.,1997) FIPs,with a molecular weight of about 13 kDa,compose of FIGURE 4.The tetrameric structure of FIP-gmi. 110-114 amino acids.Histidine,cysteine and methionine are absence,instead FIPs are rich in aspartic acid and valine. The N-terminal amino acids are acetylated (Li et al.,2011). LZ-8 is a glycoprotein containing low content of carbohydrate that is about 1.3%,and its isoelectric point is 4.4(Kino et al., 1989). As have mentioned,FIPs have higher homology in their primary structure.The sequences of LZ-8(FIP-glu)and FIP- gts even have more or less the same amino acids.Natural FIPs exist mostly in the form of homodimer.The predicted secondary structures show that FIPs are rich in B-sheet structure that contains completely conserved amino acid sequences.These sequences are supposed to have a direct relationship with the function of FIPs.Based on the studiesFungal immunomodulatory proteins 3 Amino-acid Composition and Structural Characteristic of FIPs: The amino acid composition and structure of protein and structure of proteins resulted in different physical properties, chemical properties and physiological functions. Seven FIP genes have been isolated from various mushrooms respectively. The corresponding seven proteins encoded by these genes are known as LZ-8 (FIP-glu), FIP-gts, FIP-fve, FIP-vvo, FIP-gja, FIP-gmi and FIP-gsi (Zhou et al., 2009; Li et al., 2011). Among the seven FIPs, only four FIPs, LZ-8 (FIP-glu), FIP￾gts, FIP-fve, and FIP-vvo, are isolated directly from the fruit￾bodies or mycelia of natural mushrooms. Their basic characteristics are summarized in Table 1. The others are obtained by means of the recombinant DNA technology based on their homologous gene sequences. The primary structures of FIPs have high homology after aligning of amino acid sequences, generally up to 60-70% (Figure 2). FIPs, with a molecular weight of about 13 kDa, compose of 110-114 amino acids. Histidine, cysteine and methionine are absence, instead FIPs are rich in aspartic acid and valine. The N-terminal amino acids are acetylated (Li et al., 2011). LZ-8 is a glycoprotein containing low content of carbohydrate that is about 1.3%, and its isoelectric point is 4.4 (Kino et al., 1989). As have mentioned, FIPs have higher homology in their primary structure. The sequences of LZ-8 (FIP-glu) and FIP￾gts even have more or less the same amino acids. Natural FIPs exist mostly in the form of homodimer. The predicted secondary structures show that FIPs are rich in β-sheet structure that contains completely conserved amino acid sequences. These sequences are supposed to have a direct relationship with the function of FIPs. Based on the studies β-turn in the predicted secondary structure (Lin et al., 1997). The basic structure is crucial to forming homodimer, recognizing cell surface, and playing a role in immune regulation, and is necessary for the immunomodulatory function of FIPs. Lin et al. has analyzed the N-terminal sequence of FIP-gts via yeast two-hybrid and site-directed mutagenesis techniques (Lin et al., 1997). 1.7Å structure of FIP-fve, studied by Paaventhan et al., showed that the dimmer formation was stabilized predominantly by hydrophobic interactions among the N-terminal helices (Figure 3), and was presumed to play a role in the immune function. Each monomer consists of an N-terminal α-helix, followed by a fibronectin III (FNIII) fold, which is a transition formation between seven β-stranded s-types and eight β-stranded h-type topologies (Paaventhan et al., 2003). Lacking of cysteine, FIPs may depend on other forces such as hydrophobic forces between β-sheets to maintain the appropriate conformation. At the same time, the structure of FIPs is highly similar with the immunoglobulin heavy chain variable region (IgVH) containing the complementary sites of antigen (complementarity determining domain) and composing antibody-antigen binding site with the light chain variable region, which could be specifically bound to antigen and then trigger immune response. Therefore, the similarities and differences between the structures of FIPs and IgVH will be helpful to further explore on the classification and identification of FIPs as well as the mechanism of immune regulation. FIGURE 2. The blast result of FIPs Amino acid sequences. Name Molecular Number of Mushroom Reference Weight(KD) Amino Acid LZ-8 (FIP-glu) 13.100 110 G. lucidum (Kino et al., 1989) FIP-gts 13.000 110 G. tsugae (Lin et al., 1997) FIP-fve 12.704 114 F. velutipes (Ko et al., 1995) FIP-vvo 12.667 112 V. volvacea (Hsu et al., 1997) TABLE 1. Basic characteristics of natural FIPs. FIGURE 3. The dimmer structure of FIP-fve. FIGURE 4. The tetrameric structure of FIP-gmi. its function is closely related to each other. Different spatial on FIP-gts, there are two α -helices, seven β-sheets, and one