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J B Ulmer

Publications and source records attributed to J B Ulmer.

74 records · Page 5Linked to original sources
PubMed1986

In vivo phosphorylation of myelin basic proteins: single and double isotope incorporation in developmentally related myelin fractions.

The phosphorylation of myelin basic proteins (MBPs) was studied in developing mouse brain. Based on our previous work we postulated that phosphorylation of MBPs takes place prior to their appearance in the myelin compartment as well as within the myelin sheath. To further test this hypothesis we utilized a subfractionation protocol that yields brain fractions enriched in myelin membranes of differing developmental stages. Incorporation of radioactive phosphate into MBPs was studied in each of the subcellular fractions. After 5- and 15-min incubations of isotope in vivo the highest specific radioactivities (SAs) of MBPs were found in the least mature myelin fractions. Incorporation of 32P in MBPs was greater into serine residues than threonine residues in all of the subcellular fractions studied. The relative turnover of MBP phosphates was studied in each of the subcellular myelin fractions using a time-staggered, double isotope methodology. The most rapid equilibration of MBP phosphates with the trichloroacetic acid (TCA)-soluble phosphate pool occurred in the most mature myelin fractions indicating that the highest turnover of MBP phosphates occurs in the most mature myelin fractions. The SAs and turnover rates of each of the four commonly observed mouse MBPs (14, 17, 18.5, and 21.5 kDa) were similar in any particular subfraction demonstrating that the MBP phosphotransferase system(s) acts on each of the MBPs in a similar manner.

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PubMedDate not supplied

In vivo phosphorylation of myelin basic proteins in developing mouse brain: evidence that phosphorylation is an early event in myelin formation.

Myelin basic proteins (MBPs) can be detected in 5-day mouse brain, even though there is very little myelin present. In addition to the 4 MBP components (with molecular weights of 14, 17, 18.5 and 21.5 kilodaltons), that are commonly observed, other larger MBP-related polypeptides are also present. We have investigated the possibility of MBP phosphorylation at early stages of development in order to establish the point at which this modification occurs in the assembly of myelin. In vivo isotope studies show that in the 5-day mouse brain 14-, 17-, 18.5- and 21.5- kilodalton MBPs are phosphorylated and that they may be present in an immature form of myelin. Larger MBP-related proteins with a molecular weight of 35 and 42 kilodaltons are also phosphorylated but appear to be present mostly in nonmyelin structures or compartments.

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