TITLE:
Tropomyosin Isoform Expression in the Adductor Muscle of the Japanese Pearl Oyster, Pinctada fucata
AUTHORS:
Daisuke Funabara, Ayaka Ohta, Jungo Sueyoshi, Satoshi Kanoh
KEYWORDS:
Adductor Muscle, Alternative RNA Processing, Catch Contraction, Pearl Oyster, Tropomyosin
JOURNAL NAME:
American Journal of Molecular Biology,
Vol.9 No.1,
December
11,
2018
ABSTRACT: We determined the full-length primary structure of
the tropomyosin (TM)-1 and -2 proteins from the adductor muscle of the Japanese
pearl oyster Pinctada fucata (Pifuc-TM-1 and Pifuc-TM-2), and found that they are each composed of 284
amino acid residues. We predicted the gene structure of P. fucata TM (Pifuc-TM) using Splign alignment of our cDNA with genomic sequences and
elucidated that Pifuc-TM consists of 10 exons. Exons 1 - 3 and
5 - 10 are used to transcribe Pifuc-TM-1 mRNA, and exons 1 - 4 and 6 - 10
are used to transcribe Pifuc-TM-2 mRNA. Both genes share the same
start and stop codons located in exon 1 and exon 10, respectively. Using
quantitative real-time PCR, we determined that the Pifuc-TM-1 gene was
mainly expressed in adductor phasic muscle, and at a relatively weaker level in
adductor catch muscle, whereas the Pifuc-TM-2 gene was expressed equally in both
phasic and catch muscles. They were weakly expressed in gill and mantle.
Immunoblot analysis using anti-Pifuc-TM-1 and anti-Pifuc-TM-2 antibodies
revealed that adductor phasic muscle contained Pifuc-TM-1, while adductor catch
muscle contained both Pifuc-TM-1 and Pifuc-TM-2. Differential scanning
calorimetry (DSC) analysis was carried out for Pifuc-TM-1 and Pifuc-TM-2
expressed in bacteria, as well as TM purified from P. fucata phasic and catch
muscle tissues (phasic-TM and catch-TM). The DSC data indicated that phasic-TM
was mainly composed of Pifuc-TM-1, whereas catch-TM contained Pifuc-TM-1 and
Pifuc-TM-2. These findings suggest that the distribution of Pifuc-TM-1 and
Pifuc-TM-2 in adductor muscle is specific to the
muscle fiber type, and reflects the properties of each.