Table schema:
CREATE TABLE table_16849531_2 (ncbi_accession_number__mrna_protein_ VARCHAR, length__bp_aa_ VARCHAR)

Question: What is the NCBI Accession Number for the length of 5304bp/377aa?
SQL: SELECT ncbi_accession_number__mrna_protein_ FROM table_16849531_2 WHERE length__bp_aa_ = "5304bp/377aa"