  Proteins are known to locate their specific targets on DNA up to two orders
of magnitude faster than predicted by the Smoluchowski three-dimensional
diffusion rate. One of the mechanisms proposed to resolve this discrepancy is
termed "intersegment transfer". Many proteins have two DNA binding sites and
can transfer from one DNA segment to another without dissociation to water. We
calculate the target search rate for such proteins in a dense globular DNA,
taking into account intersegment transfer working in conjunction with DNA
motion and protein sliding along DNA. We show that intersegment transfer plays
a very important role in cases where the protein spends most of its time
adsorbed on DNA.
