Disclosed are a protein encoded by any one of nucleic acids (i) to (iv): (i) a nucleic acid having a base sequence of SEQ ID NO: 1 (ii) a nucleic acid encoding a protein having an amino acid sequence of SEQ ID NO: 2 (iii) a nucleic acid encoding a dragline protein and having a sequence identity of 90% or more with the nucleic acid (i) (iv) a nucleic acid which encodes a dragline protein and hybridizes with a complementary chain of the nucleic acid (i) under stringent conditions, and a silk thread containing the protein.
