Genomic structure of the amphioxus calcium vector protein

Area of Science:

• Evolutionary biology
• Molecular biology
• Biochemistry

Background:

• Calcium vector protein (CaVP) is a unique EF-hand Ca(2+)-binding protein found in amphioxus.
• Its precise function as a Ca(2+) signal transducer and its evolutionary relationships are not well understood.

Purpose of the Study:

• To investigate the evolutionary origins and relationships of CaVP.
• To elucidate the gene structure of CaVP and compare it with related Ca(2+)-binding proteins.

Main Methods:

• Sequencing of CaVP cDNAs from two amphioxus species (Branchiostoma lanceolatum and B. floridae).
• Gene structure elucidation of B. floridae CaVP, including exon-intron organization.
• Comparative analysis of intron positions with calmodulin, troponin C, and Spec proteins.

Main Results:

• High sequence identity (96.5% cDNA, 98.2% amino acid) between CaVP from the two studied amphioxus species.
• The CaVP gene comprises seven exons and six introns.
• Four intron positions are conserved with calmodulin, troponin C, and Spec proteins, indicating CaVP belongs to the troponin C superfamily.
• One intron is unique to CaVP, potentially marking its lineage.
• The position of another intron is not conserved, suggesting evolutionary events like intron sliding or addition.

Conclusions:

• CaVP is likely a member of the troponin C superfamily, based on conserved intron positions.
• The unique intron in CaVP may serve as a lineage-specific marker.
• Gene structure analysis provides insights into the evolution of Ca(2+)-binding proteins.