Primary structure of nuclease-like proteins from Eisenia foetida

Yu Bao-feng; Liu Zhi-zhen; Zhang Yue-hong; Xie Jun; Cheng Niu-liang; Wang Jian-hua; Niu Bo

doi:10.3969/j.issn.2095-4344.2014.15.016

Abstract：BACKGROUND:A group of nuclease-like proteins were previously purified from Eisenia foetida tissues, exploring primary structures of these proteins wil help to uncover basic structure characteristics of them and provide foundations for the study addressing the relationship of their structures and functions. <br> OBJECTIVE:To explore primary structures of nuclease-like proteins EWD1 and EWD2. <br> METHODS:Edman degradation method was used to sequence the N-terminal amino acids of EWD1 and EWD2, acid hydrolisis method was used to analyze amino acid compositions of EWD1 and EWD2, LC-MS/MS was used to analyze some peptide sequences within the proteins, and MALDI-TOF-MS was used to calculate the number of the disulfide bonds and the contents of polysaccharides. <br> RESULTS AND CONCLUSION:Among the amino acid compositions in EWD1 and EWD2, the sum contents of aspartate and asparagines were the highest (al nearly 10%), the contents of hydrophobic amino acids were also high, and the contents of cysteine was low. The EWD1 and EWD2 had similar amino acid compositions with other nucleases. Edman degradation results showed that, the N-terminal sequences of the large subunit of EWD1 were in turn as fol ows:D, E, W, V, Y, P;the N-terminal sequences of EWD2 were as fol ows:L, L, G, P, Y, K, P, K, C. The results of LC-MS/MS indicated the two proteins were novel proteins;MALDI-TOF-MS results showed that 8 cysteine residues formed 4 disulfide bonds in EWD1, 6 cysteine residues formed 3 disulfide bonds in EWD2. EWD1 and EWD2 were al glycoproteins, the content of polysaccharides was 17.3%in EWD1 and 15.6%in EWD2.