TITLE:
Molecular Cloning and Tissue Distribution of Troponin C from the Japanese Pearl Oyster, Pinctada fucata
AUTHORS:
Daisuke Funabara, Yoshinori Urakawa, Satoshi Kanoh
KEYWORDS:
Adductor Muscle, Catch Contraction, EF-Hand, Troponin, Troponin C
JOURNAL NAME:
American Journal of Molecular Biology,
Vol.8 No.3,
July
5,
2018
ABSTRACT: Troponin C (TnC) is one of the subunits of troponin.
Troponin, which is activated by Ca2+ binding, is a thin
filament-associated regulator of vertebrate striated muscle contraction. The
function of TnC in vertebrates has been characterized in detail, but the role
of TnC in molluscan muscles is still unclear. In this work, we investigated
whether TnC plays a role in the catch contraction of molluscan smooth muscle in
the bivalve Japanese pearl oyster Pinctada
fucata. We determined the full-length primary structure of the TnC protein
from the P. fucata adductor muscle (Pifuc-TnC),
and found it is composed of 150 amino acid
residues with a predicted molecular weight of 17,400. Multiple sequence
alignments indicated that it had four EF-hand motifs, but only one (site IV) was predicted
to have Ca2+-binding ability. This is analogous to characterized
TnCs from other mollusks. Three-dimensional modeling of Pifuc-TnC using
SWISS-MODEL indicated the presence of a short loop within the α-helix connecting the site II and III EF-hand motifs. We predicted the
gene structure of Pifuc-TnC using
Splign alignment of our obtained cDNA and genome sequences and elucidated that Pifuc-TnC
consists of five exons, with the start and stop codons located in exon 1 and
exon 5, respectively. Using quantitative real-time PCR, we determined that the Pifuc-TnC
gene is predominantly expressed in adductor phasic muscle and rarely in
adductor catch muscle, gill, mantle and foot. These findings suggest that TnC
may not have a role in catch muscle contraction.