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S Milburn

Publications and source records attributed to S Milburn.

7 recordsLinked to original sources
PubMed1987

Separation of protein synthesis initiation factor eIF4A from a p220-associated cap binding complex activity.

A cap binding complex activity was purified from HeLa cells by a procedure which does not depend on the use of cap-affinity chromatography. The activity co-purified with a Mr 220,000 polypeptide (p220), but not with eIF4A. The active complex therefore differs from eIF4F, the complex purified by cap analog-affinity chromatography, in that it lacks the Mr 50,000 subunit which is antigenically identical to eIF4A. The activities of eIF4F, CBP I and the eIF4A-free complex purified here were compared in a fractionated system translating capped globin mRNA. Results indicate that the two complexes have similar activities and that they perform a function which cannot be provided by CBP I alone. Cap binding complex activity can be partly separated from eIF4A activity on sucrose gradients, thus eIF4A provides a function that is distinct from cap binding complex activity. The results indicate that eIF4A can be physically separated from the cap binding complex without affecting the ability of the remaining structure to function in an in vitro translation system. They suggest that the eIF4A-free complex may provide a function that is not a property of either CBP I or of eIF4A, but may be a property of p220.

Carrier Proteins↗
PubMed1984

Demonstration in vitro that eucaryotic initiation factor 3 is active but that a cap-binding protein complex is inactive in poliovirus-infected HeLa cells.

Protein synthesis initiation factor preparations from poliovirus-infected HeLa cells have reduced ability to initiate translation on capped mRNA. The defect in initiation factors has been variously attributed to inactivation of eucaryotic initiation factor 3 (eIF3), eIF4B, or a cap-binding protein (CBP) complex. We have developed a series of in vitro protein synthesis assays to show that eIF3 is active but a CBP complex activity is inactivated after poliovirus infection. eIF3 activity, when determined in the presence of purified CBP complex, is present in sucrose gradients of factors from both infected and uninfected cells. CBP complex activity, determined in the presence of eIF3 from poliovirus-infected cells, is present in uninfected cells only and comigrates on sucrose gradient with an activity which restores the ability of crude initiation factors from infected cells to translate capped globin mRNA. This is the first demonstration by a fractionated translation system that an activity which is attributable to CBP complex is inactivated in poliovirus-infected cells. The results also indicate that eIF3 is undetectable or has greatly reduced activity in the absence of CBP complex.

Carrier Proteins↗
PubMed1983

Involvement of eukaryotic initiation factor 4A in the cap recognition process.

Antibodies against eukaryotic initiation factor 4A (eIF-4A) were used to study the involvement of this factor in recognizing the 5' cap structure of eukaryotic mRNA. We demonstrate that an approximately 50-kilodalton polypeptide present in rabbit reticulocyte ribosomal high salt wash which can be specifically cross-linked to the 5' oxidized cap structure of reovirus mRNA (Sonenberg, N. (1981) Nucleic Acids Res. 9, 1643) reacts with an anti-eIF-4A monoclonal antibody. We also show that antibodies against eIF-4A react with a 50-kilodalton polypeptide present in a cap-binding protein complex obtained by elution from a m7GTP-agarose affinity column. Comparative peptide analysis of eIF-4A and the 50-kilodalton component of the cap-binding protein complex indicates a very strong similarity between the two polypeptides.

Adenosine Triphosphate↗
PubMed1983

A comparison of the training responses to aerobic dance and jogging in college females.

The purpose of this study was to compare the physiological alterations that occur in college females as a result of a 7-wk jogging and aerobic dance-training program. Forty-six subjects (18-29 yr) volunteered to participate and included 15 dancers, 19 joggers, and 12 controls. All subjects were given a pre- and post-VO2max treadmill test. The joggers and dancers trained 4 d/wk, 30 min/d for 7 wk at an intensity that represented approximately 83 and 84% of their initial maximal heart rates, respectively. Both experimental groups significantly (P less than 0.05) increased their VO2max, VEmax, and maximal treadmill running times and significantly (P less than 0.05) decreased their maximal heart rates as a result of the training. The control group showed no significant (P greater than 0.05) changes in any of the variables measured. It was concluded that both aerobic dance and jogging were equally effective (P less than 0.05) exercise modalities for improving cardiorespiratory endurance when performed at similar intensities, frequencies, and durations.

Adolescent↗