Some method is needed for coupling replication near the origin to the level or synthesis of DnaA. One, of many, is that the synthesis of DnaA is stimulated by an unstable protein whose gene is located near the origin and whose synthesis is shut off while its gene is hemimethylated. Mimick the normal transcription intermediate by providing the following. I reactions utilize an exogenous guanosine. The difference will be in the topology. Class I reactions involving a nucleoside, will yield linear products, whereas class II reactions, involving internal nucleotides, will generate looped products.
Proteins normally are linear polypeptide chains.
Certainly, they are synthesized that way. It is conceiveable, however, that posttranslational modification of some special oligomeric protein fuses one polypeptide chain near the middle of another in each of the oligomers. Suppose I wished to screen proteins A, B, C, for being in the vicinity of a DNA replication fork. The following is the beginning of a series of steps to do this. Gently lyse cells or nuclei.