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Proteolipids were isolated from 20 day old normal and jimpy mouse brain by extraction into chloroform-methanol (2∶1, w/v), delipidated by size-exclusion HPLC, and analyzed by SDS-PAGE, Western blots, amino acid analyses, and N-terminal sequencing. SDS-PAGE showed that a major proteolipid from jimpy mouse brain had an apparent molecular weight of ∼23 kDa, intermediate to that of PLP and DM-20 from normal mouse brain. Western blots with 3 different antibodies which recognize residues 200-224, 116-150, and 270-276 respectively recognized immunoreactive material in normal and jimpy PLP. Since antibody reactive with 270-276 did not recognize jimpy PLP, an altered C-terminus of the jimpy protein is suggested. These results demonstrated that a PLP can be partially purified from jimpy mouse brain. Amino acid analyses failed to show the predicted increase in cysteinyl residues (predicted from cDNA) in jimpy PLP. However, when jimpy brain proteolipids were subjected to N-terminal sequencing, Gly, Leu, Leu, Gly the first four amino acids of PLP were detected. Thus, the partial purification of a proteolipid from jimpy mouse brain, whose characteristics (apparent molecular weight, immunoreactivity, N-terminal sequence and relative net charge) strongly suggested that PLP of altered size is present in jimpy mouse brain. [ABSTRACT FROM AUTHOR]

The ultrastructural arrangement of membranes of the Golgi complex has been characterized in Golgi fractions isolated from rat liver. Procedures for isolation of these fractions have been modified to provide a good yield of Golgi membranes (60 to 70%) with greater than 50-fold purification of sialyl transferase, an enzyme specific for the Golgi complex. The isolated membranes appear well preserved and both the dimensions and appearance of the Golgi complex observed by negative staining and in sections of the isolated membranes correlate well with that in liver sections. The Golgi complex consists of a series of platelike structures, each consisting of a central sac or cisterna from which a network of fine tubules arises. The tubules increase in diameter towards the periphery of the plate and are associated with the formation of vacuoles or secretory vesicles. The structure of the Golgi complex has been related to its role in glycoprotein biosynthesis. [ABSTRACT FROM AUTHOR]