Binding and utilization of myoglobin by Porphyromonas gingivalis

Myoglobin was found to bind reversibly to the envelope of Porphyromonas gingivalis in a pH-dependent manner; the binding took place below neutral pHs of the incubation mixtures and myoglobin bound released from the envelope at high pHs. The amounts of myoglobin bound to 1 mg of the envelope at pH 5.0 per min under the presence of sufficient myoglobin were 1.4 microg. K(d) for the reaction at pH 5.0 was 2.2 x 10(-10) M. From the dot blot assay, myoglobin obviously bound to hemoglobin-binding protein (HbBP) of P. gingivalis, however, the amounts of myoglobin that bound to HbBP were half those of hemoglobin. One of the fractions, separated by gel filtration, of the digested materials of myoglobin by the detergent-solubilized envelope containing proteinases was found to support the growth of P. gingivalis in the iron source-depleted medium.