PERSPECTIVES AND SUMMARY ..... ... .. ..... . ..... ....... .. .. ... .. 526 THE ENZYMATIC MACHINERY: Q,B·REPLICASE AND HOST FACTOR .... 527 Identification of the Host Components and their Function in Uninftcted Escherichia coli 527 Subunit I 527 Subunits III and IV 528 The host flU:tor 529 Structure of the Replicase .... .... . .. ... .. .. .. .... ... .. .. .. .. ... . 529 Enyme shape .. . , 529 Subunit subcomplexes . ... .... .. .. .. . . .. ........ .. . . ..... .... .. ... ....... ...... .... .. . ..... .... 530 Q/J.replicase·host factor associotion ..... .. ..... ... ... ....... .. ... ...... ... .. ..... .... ... .. .. .. . .. .. . ... 531 THE GENERAL SCHEME OF IN VITRO Q/3 RNA REPLICATION ......... .. ... . 532 Plus Strands and Minus Strands .. ..... ....... . .. ........ ........ ... ......... ... ... .. .. ...... .. ... ....... . 532 Replicating RNA . .. ... . ... ... .. ... .. . . . . .... .... .. .... ... .... ..... ... . .. .. .. ... .... 532 THE ENZYMATIC MECHANISM OF IN VITRO Q/3 RNA REPLICATION .. 533 Temp/ate Specificity .. ... .. . ... . . .. .... ..... .. ... . .. . .... ........ ...... ...... ..... . .... . ..... . .. ... ..... 533 Overcoming Template Specificity .... .... ... .... . .. .. .. ... .. .. ... .. .. . ... .... .... ... .... .. .. ........ 534 Recognition of Synthetic RNAs ........ ... ... .. . ... ...... ... ...... ...... ........ .. ... . .. .. ...... ... .. .... 535

RNA replication: function and structure of Qbeta-replicase.

Bacterial proteins required for replication of phage Q ribonucleic acid. Pruification and properties of host factor I, a ribonucleic acid-binding protein.

The RNA replicating enzyme induced by RNA phage Qβ consists of a single phage specific and three host specific polypeptide chains. At least one of the host subunits is shown to be essential for enzymatic activity, and none are known subunits of E. coli DNA-dependent RNA polymerase.

Characterization of the subunits of Q-beta replicase.

We have isolated a form of Qβ replicase lacking subunit α and shown that it is deficient in the utilization of Qβ-plus strand RNA as template but competent to utilize Qβ-minus strands, poly(C) and “6-S” RNA. The functional identity of subunit α and protein-synthesis-inhibition factor i was proven by their equivalent capacity to restore full Qβ RNA-directed activity of α-less replicase.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1972.tb02498.x

Reconstitution of Qβ Replicase Lacking Subunit α with Protein-Synthesis-Interference Factor i

Site-specific interaction of Qbeta host factor and ribosomal protein S1 with Qbeta and R17 bacteriophage RNAs.

Synthesis of bacteriophage Q-beta RNA.

Phage-specific and host proteins in the replication of bacteriophage RNA.

Several steps in the synthesis in vitro of infectious bacteriophage RNA can now be described. The reaction catalyzed by the Qβ RNA polymerase is known to involve several components, including the enzyme, host cell factors, Qβ RNA template, and the strand complementary to the Qβ RNA. The interaction of these components and the mechanims of the reaction appears to be considerably more complex than was proposed in earlier models.

U. Rensing

Papers

Synthesis of bacteriophage Q-beta RNA.

Phage-specific and host proteins in the replication of bacteriophage RNA.

Replication of the RNA genome