The cDNA-derived amino acid sequence of hemoglobin I from Lucina pectinata

The tropical clam Lucina pectinata contains a unique hemoglobin (HbI) which serves to transport H2S to autotrophic bacteria. The cDNA-derived amino ac id sequence was obtained from overlapping clones containing the cDNA that c odes for HbI. The reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE)methods were employed to synthes ize the cDNA fragments. An initial 354-bp cDNA clone encoding 118 amino aci d residues of HbI was amplified from total RNA by RT-PCR using degenerate o ligonucleotides. Gene-specific primers derived from the HbI-partial cDNA se quence were used for obtaining the 5' and 3' ends of the cDNA by RACE. The length of the HbI cDNA, estimated from sequence analysis of overlapping clo nes, was 1322 bp for the full-length cDNA. The coding region of the full-le ngth cDNA codes for 143 amino acid residues. The most conserved amino acid residues in HbI from Lucina pectinata were identified by a multiple alignme nt with nonvertebrate globin sequences.