An inhibitor kappaB homologue from bay scallop Argopecten irradians.
IkappaB is an important member of NF-kappaB pathway in the innate immune system. In the present study, the full-length cDNA sequence encoding IkappaB protein (designated AiIkappaB) was isolated from bay scallop Argopecten irradians. The complete sequence of AiIkappaB cDNA containing a 5' untranslated region (UTR) of 237 bp, a 3' UTR of 1023 bp with a poly (A) tail, and an open reading frame (ORF) of 1086 bp encoding a polypeptide of 361 amino acids with the predicted molecular weight of 39.9 kDa and theoretical isoelectric point of 4.7. Six ankyrin repeats which were necessary for specific binding to NF-kappaB and two potential phosphorylation sites responsible for IkappaB degradation were identified in the N-terminus of AiIkappaB. No PEST domain but a phosphorylation site motif (S(357)DSD(360)) was present at the C-terminus of AiIkappaB. Predicted three-dimensional structure of AiIkappaB shared high similarity with mammalian IkappaBalpha. Similarity and phylogenetic analysis revealed that AiIkappaB was clustered into IkappaBs from invertebrate. All these typical characteristics indicated that the AiIkappaB should be classified into IkappaB family proteins. Quantitative real-time RT-PCR was employed to assess the mRNA expression of AiIkappaB in various tissues and its temporal expression in haemocytes of scallops challenged with Listonella anguillarum. The mRNA transcript of AiIkappaB could be detected in all the examined tissues with highest expression level in hepatopancreas. Bacteria infection inhibited the transcription level of AiIkappaB. The results suggested the involvement of AiIkappaB in responses against bacterial infection and further highlighted its functional importance in the immune system of A. irradians.
Mu
Changkao
C
The Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd., Qingdao 266071, China.
Yu
Yundong
Y
Zhao
Jianmin
J
Wang
Lingling
L
Song
Xiaoyan
X
Zhang
Huan
H
Qiu
Limei
L
Song
Linsheng
L
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006434:Hemocytes / Q000276:immunology / Q000382:microbiology; D020672:I-kappa B Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D053526:Listonella / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D049897:Pectinidae / Q000145:classification / Q000235:genetics* / Q000276:immunology*; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D020672:I-kappa B Proteins