ELECTROSPRAY-IONIZATION MASS-SPECTROMETRIC COMPOSITION OF THE 400 KDAHEMOGLOBIN FROM THE POGONOPHORAN OLIGOBRACHIA-MASHIKOI AND THE PRIMARY STRUCTURES OF 3 MAJOR GLOBIN CHAINS
Hj. Yuasa et al., ELECTROSPRAY-IONIZATION MASS-SPECTROMETRIC COMPOSITION OF THE 400 KDAHEMOGLOBIN FROM THE POGONOPHORAN OLIGOBRACHIA-MASHIKOI AND THE PRIMARY STRUCTURES OF 3 MAJOR GLOBIN CHAINS, Biochimica et biophysica acta. Protein structure and molecular enzymology, 1296(2), 1996, pp. 235-244
Maximum entropy analysis of the electrospray ionization mass spectra o
f the native, carbamidomethylated, reduced and reduced and carbamidome
thylated forms of the extracellular ca. 400 kDa hemoglobin of the pogo
nophoran Oligobrachia mashikoi has shown it to consist of eight globin
chains: (a1-a5), 14861.1, 14937.1, 15040.7, 15070.6 and 15310.6 Da an
d b-d1, 15173.2, 15605.1 and 14775.4 Da, respectively. Although chains
a1-a5 are monomeric, chains b+c form a disulfide-bonded dimer of 3077
6.8 Da and chains b+c+d1 form a disulfide-bonded trimer of 45551.9 Da.
The major chains a5, b and c were separated by reverse-phase chromato
graphy, and their cDNA's amplified by PCR using redundant oligomers ba
sed on their N-terminal amino-acid sequences. The complete amino-acid
sequences of chains a5 (142 residues), b (140 residues) and c (147 res
idues) were derived from protein and cDNA sequencing and represent the
first pogonophoran globin sequences. They have a high percent identit
y (35-52%) with the globin chains of the approximate to 3500 kDa hexag
onal bilayer hemoglobins from the annelids Lumbricus and Tylorrhynchus
and the vestimentiferan Lamellibrachia, suggesting a very close relat
ionship among the phyla Annelida, Pogonophora and Vestimentifera. Two
free cysteine residues (Cys-73 and Cys-83), which we proposed to be th
e most probable candidates for the sulfide-binding sites in the Lamell
ibrachia chains (Suzuki, T., Takagi, T. and Ohta, S. (1990) Biochem. J
. 266, 221-225), are also conserved in the three chains (Cys-73 for ch
ains b and c, and Cys-83 for chain a5) of Oligobrachia hemoglobin, in
agreement with the probable role of the hemoglobin in the binding and
transport of sulfide to the symbiotic bacteria which provide the metab
olic fuel in the two phyla.