Holliday structure
The Holliday structure (English Holliday junction ) is an important intermediate step in the crossing-over . It helps in the exchange of genetic information between two homologous (similar or identical) or non-homologous DNA strands. The process is catalyzed by the enzyme recombinase . It has four subunits, two of which bind to one of the two DNA helices. This creates a recombination synapse.
The DNA exchange begins with the splitting of a single strand of each helix. The now free 5'-hydroxy groups each bind to a tyrosine residue of the subunit and are thus transported to the other side. There they bind to the 3'-phosphate group of the other double strand. One speaks of a Holliday structure.
Now a so-called branch migration can take place. In prokaryotes, the RuvAB proteins play a crucial role here. During the migration of the thighs, the Holliday junction can shift by several thousand nucleotides.
If the exchange is completed after a few 1000 nucleotides , another catalyzed cleavage takes place (in prokaryotes by the RuvC protein), and the two helices are separated from each other again. Either a patch product or a crossing-over product has now been created, depending on the angle in which the strands were separated.
The resulting strand breaks are then repaired by a ligase.
The Holliday structure is named after the Australian researcher Robin Holliday who developed the prototypical model of general recombination in 1964.
Web links
http://www.web-books.com/MoBio/Free/Ch8D2.htm
literature
- Jeremy M. Berg, John L. Tymoczko, Lubert Stryer: Biochemistry . Spektrum Akademischer Verlag, April 2003 ISBN 3-8274-1303-6
- Donald Voet, Judith G. Voet, Charlotte W. Pratt: Textbook of Biochemistry . Translation edited by Annette G. Beck-Sickinger and Ulrich Hahn. Wiley-VCH Verlag, 2002
Individual evidence
- ^ Graw, Jochen .: Genetics . 6th, revised and updated edition. Springer Berlin Heidelberg, Berlin, Heidelberg 2015, ISBN 978-3-662-44816-8 , pp. 443 .