Characterization of Spetex-1, a new component of satellite fibrils associated with outer dense fibers in the middle piece of rodent sperm flagella.
Spetex-1, which has been isolated by differential display as a haploid spermatid-specific gene, encodes a protein with two coiled-coil motifs located in the middle piece of flagella in rodent spermatozoa. The middle piece of flagella is composed of axoneme and peri-axonemal elements including outer dense fibers (ODFs) and satellite fibrils. Pre-embedding immunoelectron microscopy clearly demonstrated that Spetex-1 is located at satellite fibrils associated with ODFs in the middle piece of flagella of rat spermatozoa. Extraction of Spetex-1 from spermatozoa by SDS or urea required dithiothreitol, suggesting crosslinking by disulfide bond is involved in the assembly of satellite fibrils containing Spetex-1. We identified putative Spetex-1 orthologs in many animal species, and both cysteine residues and coiled-coil motifs were well conserved in mammalian orthologs of Spetex-1. When Spetex-1 was co-transfected into COS-7 cells with myc-tagged Tektin4, another filamentous protein associated with ODFs, the two molecules were co-localized in various sizes of aggregates in the cells. These data suggested that Spetex-1, a new component of satellite fibrils, might be involved in the structural stability of the sperm flagellar middle piece and functions in co-operation with Tektin4.
Kaneko
Takane
T
Laboratory of Zoology, Graduate School of Agriculture, Kyushu University, Fukuoka, Japan.
Murayama
Emi
E
Kurio
Hitoshi
H
Yamaguchi
Akihiko
A
Iida
Hiroshi
H
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D006801:Humans; D008297:Male; D016253:Microscopy, Immunoelectron; D008868:Microtubule Proteins; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D051381:Rats; D013082:Sperm Tail / Q000378:metabolism / Q000648:ultrastructure*
D003598:Cytoskeletal Proteins; D008868:Microtubule Proteins; D020033:Protein Isoforms; D011506:Proteins; C499424:Spata18 protein, rat; C044103:tektins