Molt-inhibiting hormone(MIH),which belongs to the crustacean hyperglycemic hormone(CHH)neuropeptide family,inhibits the synthesis of ecdysteroids by Y-organs.The CHH family is divided into two major groups,designated Ⅰ and Ⅱ.Group Ⅰ is composed of all CHH peptides,and Group Ⅱ is composed of most MIHs,gonad-inhibiting hormone(GIH)and mandibular organ-inhibiting hormone(MOIH).The Group Ⅰ peptides consist of a signal sequence,a CHH precursor related peptide(CPRP)and a mature hormone.The Group Ⅱ peptides have only a signal sequence and a mature hormone.The full-length molt-inhibiting hormone cDNA of Portunus trituberculatus(Pot-MIH)was cloned by the reverse transcription-polymerase chain reaction(RT-PCR)and the rapid amplification of cDNA ends(RACE).The degenerate nucleotide primers was designed based on the amino acid sequence of other crustacean MIHs.The full-length sequence of Pot-MIH cDNA(GenBank accession number:EU284117)is 1572 bp in size and consists of a 210 bp 5’-untranslated region(5’-UTR),a 342 bp open reading frame and a 3’-untranslated region(3’-UTR).The deduced polypeptide consisted of a 78-amino acid mature MIH peptide and a 35-amino acid signal ptptide.The mature Pot-MIH peptide shared twelve conserved residues(Cys7,Gly12,Arg14,Cys24,Asp26,Cys27,Asn29,Arg32,Cys40,Cys44,Phe50,and Cys53)with other crustacean MIHs.The mature Pot-MIH peptide had the Gly12 residue and the precursor lacked a CPRP sequence,both of which are characteristic of all Group Ⅱ peptides.Alignment of the amino acid sequence deduced from the full-length Pot-MIH cDNA with MIH amino acid sequences of other crustaceans revealed that they had very high identity.The identities between the putative Pot-MIH amino acid sequence with that of MIH of P.pelagicus,Callinectes sapidus,Charybdis feriatus,Cancer pagurus,C.magister,Carcinus maenas and Gecarcinus lateralis were 97%,95%,90%,82%,81%,77% and 60% respectively.Phylogenetic analysis indicates that the putative Pot-MIH cluster with other crustacean MIHs and GIHs.
