The contribution of phosphorylation and loss of COOH-terminal arginine to the microheterogeneity of myelin basic protein.

Deibler, Gladys E.; Martenson, Russell E.; Kramer, A. J.; Kies, Marian W.

doi:10.1016/s0021-9258(19)40905-8

Cited by 81 publications

(8 citation statements)

References 23 publications

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“…cpmhzmol of phosphate at each age), we calculated that the rapid incorporation of radioactive phosphate into basic proteins corresponded to ~0.25 mol of phosphate per mole of basic protein. This value is in agreement with previous reports of the level of endogenous phosphorylation of the basic protein from several species (19,40).…”

Section: Desjardins and Morellsupporting

confidence: 93%

Phosphate groups modifying myelin basic proteins are metabolically labile; methyl groups are stable.

DesJardins¹,

Morell²

1983

The Journal of Cell Biology

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Young and adult rats received intracranial injections of [3~P]orthophosphoric acid.The time course of the appearance and decay of the radioactive label on basic proteins in isolated myelin was followed for 1 too. Incorporation was maximal by 1 h, followed by a decay phase with a half-life of approximately 2 wk. However, radioactivity in the acid-soluble precursor pool (which always constituted at least half of the total radioactivity) decayed with a similar half-life, suggesting that the true turnover time of basic protein phosphates might be masked by continued exchange with a long-lived radioactive precursor pool. Calculations based on the rate of incorporation were made to more closely determine the true turnover time; it was found that most of the phosphate groups of basic protein turned over in a matter of minutes. Incorporation was independent of the rate of myelin synthesis but was proportional to the amount of myelin present. Experiments in which myelin was subfractionated to yield fractions differing in degree of compaction suggested that even the basic protein phosphate groups of primarily compacted myelin participated in this rapid exchange. Similar studies were carried out on the metabolism of radioactive amino acids incorporated into the peptide backbone of myelin basic proteins. The metabolism of the methyl groups of methylarginines also was monitored using [methyl-3H]methionine as a precursor. In contrast to the basic protein phosphate groups, both the peptide backbone and the modifying methyl groups had a metabolic half-life of months, which cannot be acounted for by reutilization from a pool of soluble precursor. The demonstration that the phosphate groups of myelin basic protein turn over rapidly suggests that, in contrast to the static morphological picture, basic proteins may be readily accessible to cytoplasm in vivo.Myelin is a compact, multilamellar extension of the membrane of specialized cells that surrounds nerve axons and functions to increase conduction velocity (for reviews, see references 15 and 43). The oligodendroglial cells in rat brain start producing myelin in substantial quantities between postnatal days l0 and 12. Myelin then accumulates at an increasingly rapid rate until 20 d of age, when the rates of synthesis and accumulation decrease progressively (47). Because of its high concentration of lipid (70%) and resulting low buoyant density, myelin of the central nervous system (CNS) is readily isolated by sucrose density gradient centrifugation (46). During the period of rapid myelin accumulation, it is possible to isolate subfractions of myelin that appear to represent different degrees of compaction and possibly different stages in the development of this specialized membrane system (3, 9, 34).In mammals, one-third of the total myelin protein of the CNS is present as a group of proteins that are closely related in sequence, the myelin basic proteins (12, 31). These proteins are located at the apposition of the very closely apposed cytoplasmic faces of the myelin me...

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Section: Desjardins and Morellsupporting

confidence: 93%

Phosphate groups modifying myelin basic proteins are metabolically labile; methyl groups are stable.

DesJardins¹,

Morell²

1983

The Journal of Cell Biology

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“…Preparation of purified MBP component 1 from rabbit brain was carried out as described previously (Deibler & Martenson, 1973; Martenson et al, 1981). Component 1 is the MBP species that contains an intact C terminus; it is not phosphorylated or deamidated (Deibler et al, 1975). Thrombic cleavage of the MBP at the Arg95-Thr96 bond and the separation and purification of the cleavage products have been described (Law et al, 1984).…”

Section: Methodsmentioning

confidence: 99%

Low-ultraviolet circular dichroism spectroscopy of oligopeptides 1-95 and 96-168 derived from myelin basic protein of rabbit

Stone¹,

Park²,

Martenson³

1985

Biochemistry

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Myelin basic protein (MBP) is a major protein constituent of the myelin sheath of the central nervous system, where it is believed to have functional alpha-helical segments. One element of the function of the protein might be "conformational adaptability" of specific regions of its amino acid sequence, since the purified protein appears to be largely devoid of ordered structure. To pursue this question, low-ultraviolet circular dichroism (CD) spectroscopy was conducted on the sequential thrombic peptides 1-95 and 96-168 of the protein in the presence of 0-92% trifluoroethanol (TFE), a solvent known to promote stable secondary structures in polypeptides. The series of CD spectra of the oligopeptides were subjected to a computerized best-fit analysis of four peptide conformations, the alpha-helix, beta-structure, beta-turn, and nonordered form. Agreement between experimental and best-fit composite spectra was achieved when standard CD curves of peptide conformations were derived from known theoretical spectra and experimental spectra of polypeptides. In dilute buffer alone, oligopeptides 1-95 and 96-168 evidence no alpha-helix but significant beta-structure (18% and 23%, respectively), as well as a predominant, extended nonordered conformation. However, the two parts of the protein differed in conformational adaptability. From 0% to 30% TFE, 96-168 exhibited concomitant transitions to 10% helix and 32% beta-structure from the nonordered form. In contrast, in 10-30% TFE, 1-95 underwent a transition to approximately 21% helix with partial loss of beta-structure as well as nonordered form; higher concentrations of TFE (40-75%) promoted additional transitions to both helix and beta-structure (totaling 33% and 25%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

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“…However, at alkaline pH (10.6), the protein resolves into several components characteristic of microheterogeneity based on net charge (Martenson et al, 1969). The BP charge microheterogeneity, which results from posttranslational modifications such as phosphorylation (Chou Deibler et al, 1975;Martenson et al, 1983), deamidation (Chou et al, 1976;Martenson et al, 1983), and in some circumstances C-terminal arginine loss (Chou et al, 1977), may alter the capacity of BP to interact with the lipid bilayer. In general, the BP used in previous studies of lipidprotein interactions (Lampe & Nelsestuen, 1982;Young et al, 1982;Lampe et al, 1983) contained all the charge isomers, and so these studies did not address the possibility of modulating effects by this charge heterogeneity on membrane organization.…”

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confidence: 99%

Effect of bovine basic protein charge microheterogeneity on protein-induced aggregation of unilamellar vesicles containing a mixture of acidic and neutral phospholipids

Cheifetz¹,

Moscarello²

1985

Biochemistry

110

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Two of the charge isomers (components 1 and 2) normally found as microheteromers of myelin basic protein were isolated, and their abilities to aggregate vesicles consisting of mixed phospholipids were studied. Component 1 (the most cationic of the microheteromers) aggregated phosphatidylcholine (PC) vesicles containing 7.8 mol% phosphatidylserine (PS) more rapidly and at lower protein concentrations than component 2, which differs from component 1 by 1 net positive charge. Modification of components 1 and 2 in vitro by phosphorylation with rabbit muscle protein kinase decreased the ability of both components to aggregate vesicles. The greater the extent of phosphorylation, the less effective were the isomers at inducing aggregation. Decreasing the charge of either component 1 or component 2 by removal of the two C-terminal arginyl residues also decreased the ability of the isomers to induce aggregation. Therefore, charge microheterogeneity, whether arising in vivo or generated in vitro, markedly affected the ability of these microheteromers to aggregate PC vesicles containing 7.8 mol% PS. Because a small difference in the charge of the protein had a marked effect on vesicle aggregation, we propose that charge microheterogeneity may play an important and dynamic role in the structure and function of normal myelin.

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The contribution of phosphorylation and loss of COOH-terminal arginine to the microheterogeneity of myelin basic protein.

Cited by 81 publications

References 23 publications

Phosphate groups modifying myelin basic proteins are metabolically labile; methyl groups are stable.

Phosphate groups modifying myelin basic proteins are metabolically labile; methyl groups are stable.

Low-ultraviolet circular dichroism spectroscopy of oligopeptides 1-95 and 96-168 derived from myelin basic protein of rabbit

Effect of bovine basic protein charge microheterogeneity on protein-induced aggregation of unilamellar vesicles containing a mixture of acidic and neutral phospholipids

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