Hexapeptide repeat structure in Dictyostelium spore coat protein

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Spore coat proteins are crucial for the structural integrity and protection of spores in Dictyostelium discoideum.
• Understanding the N-terminal sequences of these proteins can provide insights into their assembly, function, and evolution.

Purpose of the Study:

• To determine the primary amino acid sequences of the N-termini of two Dictyostelium discoideum spore coat proteins, SP60 and SP70.
• To identify any repeating motifs or unusual amino acid modifications within these sequences.
• To compare the determined sequences with known protein databases for potential homologies.

Main Methods:

• Amino acid sequencing of isolated spore coat proteins.
• Analysis of protein sequences for repeating units and post-translational modifications.
• Bioinformatic comparison with existing protein sequence databases.

Main Results:

• The N-terminus of SP60 was found to consist of perfect hexapeptide repeats (Gly-Asp-Trp-Asn-Asn-Asx-).
• The N-terminal sequence of SP70 contained a modified amino acid in two positions.
• Both SP60 and SP70 N-terminal sequences were identified as highly hydrophilic and acidic.
• A partial homology was noted between the SP60 sequence and a parvovirus capsid protein, though the latter lacks periodicity.

Conclusions:

• The N-terminal sequences of Dictyostelium discoideum spore coat proteins SP60 and SP70 reveal distinct structural features, including repetitive elements and modifications.
• These findings contribute to the understanding of spore coat protein structure and may have implications for spore development and evolution in this organism.