Structural Studies Of ’Sleeping Disease’ Related Viruses In Mud Crab

Virus is a small infectious agent that metabolizes only inside the living cells.Some viruses can cause diseases that seriously endanger human health;Some viruses can cause major diseases of economic animals and cause serious economic losses;While some viruses have some special molecular mechanisms and can become tools for molecular biology and medical science.The study of viral structure is helpful to understand the process of viral life activities,and thus to achieve the purpose of prevention and treatment of harmful viruses,which make a great significance to human beings.Mud Crab Scylla paramamosain is an important economic animal in the southeastern coast of China.It has been cultured for many years in China.However,the culture of Scylla paramamosain has been threatened by viral diseases for a long time.Studies have shown that two kinds of crab viruses:Mud crab reovirus(MCRV)and Mud crab dicistrovirus(MCDV)can cause sleeping disease in crabs,resulting in large-scale mortality and serious economic losses.In order to obtain the structural characteristics and pathogenic mechanism of the sleeping disease-related viruses and provide information for the prevention of the disease,the structures of 70nm and 30nm viruses isolated from the sick crab were solved by cryo-EM.The host binding sites,assembly,transcription and genome-release mechanisms were pursued.The results are listed below:1.3.1 A icosahedral and 3.8A D5 structures of mud crab reovirus(MCRV)were obtained,and the atomic model of four structural proteins,VP 1,VP3,VP 11 and VP 12 were built.Structure analysis reveals unique features:no intercations are observed between decamers made of VP3;Unique VP 11 play an important role in stablility of capsid and packing;TEC of MCRV are composed of by only RdRp,and arranged by D5 symmetry;A unique spike exist in N-terminal domain.Those structural feature reveals the special mechanism of capsid packing and transcription2.3.5 A icosahedral structure of mud crab dicistrovirus(MCDV)was obtained,and the atomic model of four structural proteins,VP1,VP2,VP3 and VP4 were built.A unique protrusion of VP3 covered the protuberance,which may play a role in host recognition;Research reveals the that N-terminal of VP1 and VP2,VP4,C-terminal of VP3 are related with genome unpacking3.A new virus was observed by cryo-EM single particle analysis,and the correct sequence was obtained with the help of a 3.3A structure.Based on the structural and sequential information,the virus was named as mud crab tombus-like virus.Analysis reveals that MCTV have similar structural features and packing mechanisms with Betanodavirus,Genome structure of MCTV is similar with Tombusviridae,while capsid protein is highly homologous to two nodavirus.