user: ### NOW ANSWER:
Question: What is the sequence length (aa) of the protein with the common name purple sea urchin and a divergence from human lineage less than 742.9?
Columns: ['common name', 'protein name', 'divergence from human lineage (MYA)', 'accession number', 'sequence length (aa)', 'sequence identity to human protein']
Types: ['text', 'text', 'real', 'text', 'real', 'text']
Sample row: ['Tropical Clawed Frog', 'uncharacterized protein C20orf117-like', 371.2, 'XP_002942331.1', 1584.0, '39%']
SQL:

assistant: SELECT SUM("sequence length (aa)") FROM "Table" WHERE "common name" = 'purple sea urchin' AND "divergence from human lineage (MYA)" < 742.9;