Properties of the Syrian hamster phosphomannosyl receptor: an aggregate of low molecular weight proteins.

Phosphomannosyl receptor (PMR) isolated from Syrian hamster liver was purified to apparent homogeneity by affinity chromatography and one-dimensional PAGE. On one-dimensional PAGE, the receptor migrated with a Mr approximately equal to 215,000 as detected by a silver-staining reagent or by immunoblotting [utilizing antiPMR generated against purified hamster PMR (Mr 215,000) sequentially purified by affinity chromatography and NaDodSO4/PAGE]. On two-dimensional PAGE the receptor was partially dissociated into low-molecular weight components. The protein distribution on immunoblots of two-dimensional gels of hamster liver homogenates was nearly identical to that observed for purified hamster liver PMR. When liver homogenates were subjected to one-dimensional PAGE and immunoblotted under nonreducing conditions, an intensely labeled band that migrated with an apparent Mr of 43,000-49,000 was observed; under reducing conditions a single band with a Mr of 49,000 was observed. The low molecular weight compound was present in the soluble 130,000 X g supernatant but not in the particulate fraction of liver homogenates. An immunoreactive component of similar molecular weight was also present in hamster serum and plasma. These results suggest that PMR is either an aggregate comprised of small molecular weight components or, alternatively, that a number of small molecular weight components are tightly associated with PMR.