Nitro compound detection element

A nitro compound detection element comprising an olfactory receptor protein, the olfactory receptor protein comprising

• (1) amino acid sequence 1C composed of amino acid sequence 1A of SEQ ID NO:
• 1 or amino acid sequence 1B with at least 80% identity to the amino acid sequence 1A, the amino acid sequence 1A and the amino acid sequence 1B each containing a mutation,
• wherein the amino acid sequence 1C contains mutation 1a, and the mutation 1a is deletion of a partial or entire region of the first extracellular loop;
• (2) amino acid sequence 2C composed of amino acid sequence 2A of SEQ ID NO:
• 2 or amino acid sequence 2B with at least 80% identity to the amino acid sequence 2A, the amino acid sequence 2A and the amino acid sequence 2B each containing a mutation,
• wherein the amino acid sequence 2C contains mutation 2a, and the mutation 2a is substitution 2ax or substitution 2ay,
• the substitution 2ax is substitution of at least one amino acid selected from the group consisting of L60, M138, and A152 in the amino acid sequence 2A, and
• the substitution 2ay corresponds to the substitution 2ax in the amino acid sequence 2B;
• (3) amino acid sequence 3C composed of amino acid sequence 3A of SEQ ID NO:
• 3 or amino acid sequence 3B with at least 80% identity to the amino acid sequence 3A, the amino acid sequence 3A and the amino acid sequence 3B each containing a mutation,
• wherein the amino acid sequence 3C contains mutation 3a and mutation 3b,
• the mutation 3a is substitution 3ax or substitution 3ay,
• the substitution 3ax is substitution of amino acids S114, A120, H162, V186, V352, and S368 in the amino acid sequence 3A, and the substitution 3ay corresponds to the substitution 3ax in the amino acid sequence 3B,
• the mutation 3b is substitution of a charged amino acid into an uncharged amino acid in a region from the third extracellular loop to the third intracellular loop;
• (4) amino acid sequence 4C composed of amino acid sequence 4A of SEQ ID NO:
• 4 or amino acid sequence 4B with at least 80% identity to the amino acid sequence 4A, the amino acid sequence 4A and the amino acid sequence 4B each containing a mutation,
• wherein the amino acid sequence 4C contains mutation 4a, and the mutation 4a is substitution 4ax or substitution 4ay,
• the substitution 4ax is substitution of amino acids M61, C104, R112, G181, V189, and I327 in the amino acid sequence 4A, and the substitution 4ay corresponds to the substitution 4ax in the amino acid sequence 4B;
• or
• (5) amino acid sequence 5C composed of amino acid sequence 5A of SEQ ID NO:
• 5 or amino acid sequence 5B with at least 80% identity to the amino acid sequence 5A, the amino acid sequence 5A and the amino acid sequence 5B each containing a mutation,
• wherein the amino acid sequence 5C contains mutation 5a, and the mutation 5a is substitution 5ax or substitution 5ay,
• the substitution 5ax is substitution of amino acid L178 in the amino acid sequence 5A, and the substitution 5ay corresponds to the substitution 5ax in the amino acid sequence 5B.