Download For the existence of life proteins are one of the most important

The ribosomal protein L7/ L12
Karina Wagner
For the existence of life proteins are one of the most important substances and without them life
is not possible. Proteins are three dimensional makromolecules built of chains of amino acids
and cells produce these amino acid chains in organelles called ribosomes. Even if ribosomes are
the protein machineries of the cells they themselves contain proteins. The other component of the
ribosome is the ribosomal RNA, a nucleic acid. The ribosome (70S) of bacteria (prokaryotes)
consists of a large (50S) and a small (30S) subunit as seen in the figure. The S refers to the size
in Svedberg units. One of the prominent features of the large subunit of the ribosome is the
“stalk”. The main component of the stalk in Escherichia coli is the protein named L7/ L12. It is
the only protein of the ribosome that occurs in more than one copy and it is present as a dimer of
dimers which refers to four copies. This protein is very well studied by different biochemical
methods but still it is not clear how the dimers are orientated. The intact full length dimers are
too big and flexible for structural studies by X- ray, crystallography or NMR. The aim of this
project was to modify the protein on the gene level by cloning the first 38 amino acid residues
from the N- terminal domain of the L7/ L12 protein which will form the N- terminal dimer.
Because of the small size it is a much easier target for structural studies than the whole protein so
that the mode of dimerization can hopefully be solved.
Stalk
Figure 1: Bacterial ribosome (70S)
Degree project in biology, University of Uppsala, spring 2003
Examensarbete i biologi, 10p
Department of Cell and Molecular Biology
Supervisor: Dr. Suparna Sanyal