title: Mechanism study on a new antimicrobial peptide Sphistin derived from the N-terminus of crab histone H2A identified in haemolymphs of Scylla paramamosain.
abstract: Histone H2A is known to participate in host immune defense through generating special antimicrobial peptides (AMPs), for which it has been an interesting research focus to characterize this kind of peptides in vertebrates and invertebrates. Although thousands of AMPs have been reported in variety of life species, only several AMPs are known in crabs and in particular no H2A-derived AMP has yet been reported. In the present study, a 38-amino acid peptide with antimicrobial activity was determined based on the sequence analysis of a histone H2A identified from the mud crab Scylla paramamosain. The histone H2A derived peptide was an AMP-like molecule and designated as Sphistin. Sphistin showed typical features of AMPs such as amphiphilic α-helical second structrue and positive charge net. The synthetic Sphistin exerted high antimicrobial activity against Gram-positive, Gram-negative bacteria and yeast, among which Aeromonas hydrophila, Pseudomonas fluorescens and Pseudomonas stutzeri are important aquatic pathogens. Leakage of the cell content and disruption of the cell surface were observed in bacterial cells treated with Sphistin using scanning electron microscopy. It was proved that the increasing cytoplasmic membrane permeability of Escherichia coli was caused by Sphistin. Further observation under confocal microscopy showed that Sphistin could combine onto the membrane of Staphylococcus aureus, E. coli MC1061 and Pichia pastoris but not translocate into the cytoplasm. Moreover, the affinity of Sphistin with either LPS or LTA was also testified that there was an interaction between Sphistin and cell membrane. Thus, the antimicrobial mechanism of this peptide likely exerted via adsorption and subsequently permeabilization of the bacterial cell membranes other than penetrating cell membrane. In addition, synthetic Sphistin exhibited no cytotoxicity to primary cultured crab haemolymphs and mammalian cells even at a high concentration of 100 μg/mL for 24 h. This is the first report of a histone-derived Sphistin identified from S. paramamosain with a specific antimicrobial activity and mechanism, which could be a new candidate for future application in aquaculture and veterinary medicine.
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Bei
authors.initials: B
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Dan-Qing
authors.initials: DQ
authors.lastname: Fan
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Ke-Xin
authors.initials: KX
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Zhong-Guo
authors.initials: ZG
authors.lastname: Shan
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Fang-Yi
authors.initials: FY
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Hou
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China.
authors.forename: Ling
authors.initials: L
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian 361102, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian 361102, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian 361102, PR China. Electronic address: wkjian@xmu.edu.cn.
authors.forename: Ke-Jian
authors.initials: KJ
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D060829:Arthropod Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D001483:Base Sequence; D003386:Brachyura / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000821:virology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D046848:White spot syndrome virus 1 / Q000502:physiology*; D015003:Yeasts / Q000187:drug effects
chemical_list: D023181:Antimicrobial Cationic Peptides; D060829:Arthropod Proteins; D018076:DNA, Complementary; D006657:Histones; D012333:RNA, Messenger
keywords: Antimicrobial activity; Antimicrobial mechanism; Cytotoxicity; Histone; Scylla paramamosain; Sphistin