摘要:

Evidence suggests that desmin, titin and nebulin, three recently discovered proteins, have cytoskeletal roles in muscle cells. The three proteins have been purified from mature skeletal muscle and partially characterized. Properties of the three proteins are described, with special regard to their probable roles and importance in maintaining muscle cell integrity. Results will be shown that demonstrate ability of purified desmin to self‐assemble into synthetic 10‐nm (intermediate) diameter filaments. Taken together with immunoelectron microscope results (Richardson et al. 1981), it is evident that desmin is the major component of 10‐nm filaments of mature skeletal muscle cells and that the desmin filaments link adjacent myofibrils at their Z‐line levels and seemingly tie the myofibrils into the cell cyto‐skeleton. Desmin is degraded at about the same rate as is the highly susceptible troponin‐T in bovine semitendinosus muscle postmortem. Alterations in desmin and other recently discovered cytoskeletal proteins would be expected to disrupt muscle cell integrity and to have marked effects on properties of muscle important to its

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00310.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Protein‐protein interaction of bovine natural actomyosin (NAM) was studied by means of optical density changes resulting from discrete particle formation in the temperature range of4°C to 70°C. From Arrhenius plots, the apparent heat of activation (ΔHa) at pH 5.5 (17.1 kcallmole) was significantly (P<0.05) lower than activation energies in the pH range of 6.0 to 7.5. The lower Δ Haresulted in initiation of protein‐protein interaction at a temperature near 16°C at pH 5.5, whereas interaction did not proceed until the temperature approached 37°C at pH 6.0 and above. Derivative curves (dOD/dT) at pH 5.5 and 6.0 showed two distinct NAM thermal transition regions. Tm1occurred at 43.0°C at pH 5.5 and 48.5°C at pH 6.0, with the 5.5°C difference possibly arising from effects of proton binding in altering protein conformation. Only a 1.5°C difference in Tm2(56.0°C at pH 5.5 versus 57.5°C at pH 6.0) was found. Although the overall heat‐mediated NAM aggregation (in dilute solution) was found to follow first order kinetics by two evaluation methods, the existence of two thermal transitions supports a two‐step reaction mechanism proposed for the formation of protein gels (in higher conce

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00311.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The properties of tomato polygalacturonases at two ripening stages were investigated. Two isoenzymes, PG I and II, were isolated from underripe fruits with an orange skin color. Fully ripe fruits contained only polygalacturonase II. PG I and II were purified by chromatography on DEAE‐Sephadex A‐50, Sephacryl S‐200 and CM‐agarose chromatography. PG I had a Mrof 199,500 as determined by Sephacryl S‐300 gel filtration and was 50% inactivated at 66.5°C and pH 4.5 after incubation for 5 min. It had an activation energy (Ea) of 16.8 Kcallmol (70.3 times 103Jlmol), Vmaxof 27.7 units/mg protein and Kmvalue of 7.5 times 10−2mM polygalacturonic acid. PG II had a Mrof 45,700 and was 50% inactivated at 58°C under the same conditions. Both isozymes had a pH optimum of 4.6. PG II had an Eavalue of 14.8 Kcallmol (61.9 times 103Jlmol), Vmaxvalue of 58.8 units/mg protein and Kmvalue of 3.8 times 10−2mM polygalacturonic acid. PGI gave rise to only one band during electrophoresis in polyacrylamide gels, whereas PG II showed one major and one minor band both with PG activity. Gel electrophoresis in the presence of sodium dodecyl sulfate resulted in two major bands (Mr= 47,500 and 41,000) for PG I and only one major band (Mr= 47,500) for PG II. PG I is composed of several subunits, all of which ar

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00312.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of maleic hydrazide treatment on the contents of total and non‐protein nitrogen, protein and minerals was assessed on cortex and pith tissues of two potato varieties (Katahdin and Kennebec) grown at two locations (Long Island and Ithaca, NY). Maleic hydrazide significantly increased (p<0.01) the total and non‐protein nitrogen of cortex tissue but showed no significant effect on protein and mineral contents. Sprouts and bud tissue from Katahdin and Kennebec tubers grown at Ithaca were assessed for mineral composition. In both varieties the amounts of calcium, magnesium, manganese and zinc in sprouts were significantly increased (p<0.01) by maleic hydrazide treatment. No significant effect of MH on mineral content of bud tissue was obser

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00313.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Book reviewed in this article:Proteins.Edited by P. F. Fox.Food Proteins.Edited by P. F. Fox and J. J. Condon.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00314.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1984.tb00309.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY