Structural studies on dendrostomum pyroides hemerythrin

Abstract

The N-terminal sequence has been determined for the first 34 residues of the nonheme iron respiratory protein hemerythrin from the sipunculid worm Dendrostomum pyroides using an automated sequencer. Additionally, the composition and sequence of the tryptic peptides of D. pyroides hemerythrin have been compared to the previously determinedIn a previous study we reported the physicochemical properties of the hemerythrin from the sipunculid worm Dendrostomum pyroides. The pigment of this species was shown to have a molecular weight of approximately 100,000 and to consist of eight subunits. Amino acid analysis, peptide mapping, and immunological studies indicated that D. pyroides hemerythrin was very similar in structure to the hemerythrin from another sipunculid worm, Golfingia gouldii. The amino acid sequence of the Golfingia pigment has been reported by Klotz and his coworkers (Groskopf et al., 1966a,b; Subramanian etal., 1968;Klippenstein et al., 1968).This paper is concerned with the N-terminal sequence and with the composition and sequence of typtic peptides of D. pyroides hemerythrin and compares the structure of this protein to that from G. gouldii. Materials and MethodsD. pyroides were obtained from Pacific Bio-Marine Supply Co., Venice, Calif. G. gouldii were from the Marine Biological Laboratory, Woods Hole, Mass. Hemerythrin was prepared as described previously (Ferrell and Kitto, 1970) and converted into the apoprotein by the procedure of Groskopf et al. (1966a). Chemicals for the automated sequence analysis were purchased as a kit from Beckman Instruments, Palo Alto, Calif.Amino Acid Analysis. Amino acid analyses were performed according to the standard methods of Moore et al. (1958), using a Beckman-Spinco automatic amino acid analyzer. Iron-free hemerythrin, prepared according to Groskopf et al. (1966a), was hydrolyzed at 110°in 6 n HC1 in sealed, evacuated tubes for 24, 48, and 72 hr. Serine and threonine were