title: Amphioxus connectin exhibits merged structure as invertebrate connectin in I-band region and vertebrate connectin in A-band region.
abstract: Connectin is an elastic protein found in vertebrate striated muscle and in some invertebrates as connectin-like proteins. In this study, we determined the structure of the amphioxus connectin gene and analyzed its sequence based on its genomic information. Amphioxus is not a vertebrate but, phylogenetically, the lowest chordate. Analysis of gene structure revealed that the amphioxus gene is approximately 430 kb in length and consists of regions with exons of repeatedly aligned immunoglobulin (Ig) domains and regions with exons of fibronectin type 3 and Ig domain repeats. With regard to this sequence, although the region corresponding to the I-band is homologous to that of invertebrate connectin-like proteins and has an Ig-PEVK region similar to that of the Neanthes sp. 4000K protein, the region corresponding to the A-band has a super-repeat structure of Ig and fibronectin type 3 domains and a kinase domain near the C-terminus, which is similar to the structure of vertebrate connectin. These findings revealed that amphioxus connectin has the domain structure of invertebrate connectin-like proteins at its N-terminus and that of vertebrate connectin at its C-terminus. Thus, amphioxus connectin has a novel structure among known connectin-like proteins. This finding suggests that the formation and maintenance of the sarcomeric structure of amphioxus striated muscle are similar to those of vertebrates; however, its elasticity is different from that of vertebrates, being more similar to that of invertebrates.
authors.affiliation: Department of Biology, Graduate School of Science, Chiba University, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ohtsuka
authors.forename: Akira
authors.initials: A
authors.lastname: Hanashima
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kubokawa
authors.forename: Yulong
authors.initials: Y
authors.lastname: Bao
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Tando
authors.forename: Junki
authors.initials: J
authors.lastname: Kohmaru
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakaya
authors.forename: Koscak
authors.initials: K
authors.lastname: Maruyama
authors.forename: Sumiko
authors.initials: S
authors.lastname: Kimura
mesh_terms: D000818:Animals; D001483:Base Sequence; D002816:Chordata, Nonvertebrate / Q000235:genetics / Q000378:metabolism*; D064211:Connectin; D005091:Exons; D005353:Fibronectins / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry* / Q000235:genetics; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics; D017385:Sequence Homology
chemical_list: D064211:Connectin; D005353:Fibronectins; D009124:Muscle Proteins; C577285:TTN protein, human; D011494:Protein Kinases