title: A defensin from clam Venerupis philippinarum: Molecular characterization, localization, antibacterial activity, and mechanism of action.
abstract: Antimicrobial peptides (AMPs) are important mediators of the primary host defense system against microbial invasion. In the present study, we cloned and characterized a member of the invertebrate defensin from the clam Venerupis philippinarum, designated VpDef. Amino acid sequence analysis showed that VpDef was similar to defensins from marine mollusks and ticks. In non-stimulated clams, RT-PCR and immunohistochemical analysis revealed that both VpDef mRNA and the encoding peptide were constitutively expressed in hemocytes and mantles, as well as in other major tissues. VpDef transcripts were significantly induced in hemocytes at different time intervals post Vibrio anguillarum infection. The recombinant VpDef (rVpDef) showed the highest activity against Gram-positive bacteria Micrococcus luteus and less effective to Gram-negative bacteria. In addition, incubation of rVpDef with M. luteus at 1 × and 3 × MIC could induce an obvious decrease of the membrane potential and notable changes of membrane permeability in a dose-dependent manner. Membrane integrity and bacterial viability analysis also revealed that rVpDef increased the membrane permeability of M. luteus and then resulted in cell death at 2 × and 10 × MIC. Overall, these results suggest that VpDef has an important function in host defense against invasive pathogens, probably killing microbes by inducing membrane lesions.
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China; South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China.
authors.forename: Linbao
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Dinglong
authors.initials: D
authors.lastname: Yang
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: National Marine Data and Information Service, Tianjin 300171, China.
authors.forename: Zeyi
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China. Electronic address: hfwu@yic.ac.cn.
authors.forename: Huifeng
authors.initials: H
authors.lastname: Wu
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Pei
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Cong
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Li
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China.
authors.forename: Chenglong
authors.initials: C
authors.lastname: Ji
authors.affiliation: Key Laboratory of Coastal Zone Environment Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai, China; Shandong Provincial Key Laboratory of Coastal Zone Environmental Processes, YICCAS, Yantai 264003, China. Electronic address: jmzhao@yic.ac.cn.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000276:immunology*; D002463:Cell Membrane Permeability; D003001:Cloning, Molecular; D023082:Defensins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D016908:Gram-Positive Bacterial Infections / Q000276:immunology*; D006434:Hemocytes / Q000382:microbiology / Q000502:physiology*; D007113:Immunity, Innate; D050296:Microbial Viability; D016982:Micrococcus luteus / Q000276:immunology*; D008969:Molecular Sequence Data; D015854:Up-Regulation; D014733:Vibrio / Q000276:immunology*; D014735:Vibrio Infections / Q000276:immunology*
chemical_list: D023082:Defensins
keywords: Antimicrobial activity; Defensin; Membrane lesions; Molecular characterization; Tissue distribution; Venerupis philippinarum