Function and structure in phage Qβ RNA replicase: association of EF-Tu^.Ts with the other enzyme subunits

TY - JOUR

T1 - Function and structure in phage Qβ RNA replicase

T2 - association of EF-Tu.Ts with the other enzyme subunits

AU - Blumenthal, Thomas

AU - Young, Richard A.

AU - Brown, Stanley

N1 - Keywords: Binding Sites; Coliphages; Escherichia coli; Ethylmaleimide; Guanosine Triphosphate; Kinetics; Macromolecular Substances; Osmolar Concentration; Peptide Chain Elongation, Translational; Peptide Elongation Factors; Protein Binding; Q beta Replicase; RNA Nucleotidyltransferases; Sodium Chloride; Transcription, Genetic

PY - 1976

Y1 - 1976

N2 - Qbeta replicase is a complex of four nonidentical subunits readily dissociable into two subcomplexes: 30 S ribosomal protein S1 and the phage-coded polypeptide (Subunits I + II) and protein synthesis elongation factors EF-Tu and EF-Ts (Subunits III + IV). The affinity of the two subcomplexes for one another increases with increasing ionic strength. The enzyme is capable of initiation of RNA synthesis with synthetic templates only when in the low ionic strength conformation. Elongation of initiated polynucleotide chains is not affectedby ionic strength. Addition of Qbeta RNA to the enzyme also alters its quaternary structure: the EF-Tu-Ts cannot be covalently attached to the other enzyme subunits with bifunctional cross-linking reagents in the presence of RNA. This conformational change is not influenced by ionic strength. The addition of Qbeta RNA to the enzyme, does not result in the release of EF-Tu-Ts from the other enzyme subunits: whereas free EF-Tu-Ts binds GDP independently of salt concentration, this binding by Qbeta replicase is sensitive to high ionic strength and remains so in the presence of Qbeta RNA. Furthermore, RNA does not allow the release of EF-Ts from EF-Tu by GTP as measured by sensitivity of EF-Ts activity to N-ethylmaleimide.

AB - Qbeta replicase is a complex of four nonidentical subunits readily dissociable into two subcomplexes: 30 S ribosomal protein S1 and the phage-coded polypeptide (Subunits I + II) and protein synthesis elongation factors EF-Tu and EF-Ts (Subunits III + IV). The affinity of the two subcomplexes for one another increases with increasing ionic strength. The enzyme is capable of initiation of RNA synthesis with synthetic templates only when in the low ionic strength conformation. Elongation of initiated polynucleotide chains is not affectedby ionic strength. Addition of Qbeta RNA to the enzyme also alters its quaternary structure: the EF-Tu-Ts cannot be covalently attached to the other enzyme subunits with bifunctional cross-linking reagents in the presence of RNA. This conformational change is not influenced by ionic strength. The addition of Qbeta RNA to the enzyme, does not result in the release of EF-Tu-Ts from the other enzyme subunits: whereas free EF-Tu-Ts binds GDP independently of salt concentration, this binding by Qbeta replicase is sensitive to high ionic strength and remains so in the presence of Qbeta RNA. Furthermore, RNA does not allow the release of EF-Ts from EF-Tu by GTP as measured by sensitivity of EF-Ts activity to N-ethylmaleimide.

M3 - Journal article

C2 - 770471

SN - 0021-9258

VL - 251

SP - 2740

EP - 2743

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

IS - 9

ER -