Cloning mce1A gene from Nocardia seriolae and its expression

Nocardia seriolae, a bacterial fish pathogen of marine fish and freshwater fish, causing nocardiosis, can lead to mass loss of fish farming. The full-length (1 254 bp) of mce1A cDNA in N.Seriolae was cloned in this study. The Mce1A molecular weight was 43.98 kD; the theoretical isoelectric point and theoretical hydrophobic were 5.14 and 0.044, respectively. It contained 161 hydrophobic amino acids, as the hydrophobic proteins. The protein mainly consisted of random coil, and almost had no helix and folding. Sequence analysis indicates that it encoded 417 amino acids, and contained five relatively conservative domains (MCE, DUF3407, OM_asym_MlaD, Mtu_fam_mce and MlaD domain). These domains overlaped each other and contained public areas. The study constructs a phylogenetic tree based on mce1A cDNA which shows that the members of N.seriole are closely related to N.nova.We constructed a recombinant plasmid pET32a-mce1A and then transfered to E.coli BL21 (DE3) in order to obtain recombinant protein. The E.coli containing recombinant vector expressed protein of 63 kD after induction by IPTG. The results provide references for further study on pathogenic mechanism.