Sivilingeniør Kristel Berg vil fredag 7. februar klokken 10.15 offentlig forsvare sin avhandling for graden ph.d. i realfag.
Tittel på avhandlingen:
«A functional study of three bacterial nucleic acid-interacting proteins. The story of a Ferric Uptake regulator, an Oligoribonuclease and an ATP-dependent ligase»
Populærvitenskapelig sammendrag:
As the products of the instructions encoded by genes, proteins perform various activities in living cells. During protein synthesis, the genetic recipe in the DNA is copied to messenger RNA (mRNA), which is translated into the amino acid building blocks needed to produce the proteins. Proteins interacting with the genetic material in the nucleic acids RNA and DNA are crucial for cellular function and development in all living organisms.
This work investigates nucleic acid binding mechanisms and cold adaptation strategies of three different proteins that are important for various stages of normal cell development in Arctic bacteria.
The first protein studied is the DNA-interacting Ferric Uptake Regulator from the bacteria Aliivibrio salmonicida, which causes disease in farmed fish. Access to iron is important for survival of all living organisms, but also critical for the ability of pathogenic bacteria to infect humans and animals. However, since an excess of iron can be toxic, a tight control of iron levels inside cells is crucial for all organisms. In bacteria, the main controller of genes involved in iron uptake is the Ferric Uptake Regulator, which responds to signals from iron in the cellular environment. Revealing the mechanisms behind how this regulator recognize its specific genetic code in the DNA provides a potential for future development of drugs against the fish disease caused by Aliivibrio salmonicida.
The second protein studied is a DNA-joining enzyme, ATP-dependent DNA ligase, isolated from the marine bacteria Aliivibrio salmonicida, Psychromonas sp. Strain SP041 and Pseudoalteromonas arctica. These bacteria are found in cold marine environments and the use of enzymes optimized to function at lower temperatures is an important strategy to cope with such extreme conditions. Understanding how these enzymes tune their activity accordingly is of commercial interest in the field of biotechnology in particular.
The third protein studied is the RNA-degrading enzyme Oligoribonuclease, isolated from marine environmental samples outside of Svalbard by metagenomics; a method where genetic material are assessed directly. Many bacteria depends on this enzyme for the final clean-up of short RNA chains after synthesis of proteins and the mechanism behind this process is not yet fully understood. Oligoribonuclease is also of high interest in the search for novel enzymes in the field of biotechnology, especially those functioning at low temperatures.
All three proteins were cloned and produced in the bacteria E. coli by recombinant DNA technology, and purified for use in subsequent studies of protein mechanisms and structure. The enzymes ATP-dependent ligase from Aliivibrio salmonocida and Oligoribonuclease show typical features of proteins adapted to low temperatures, evident from activity and stability experiments as well structural studies. This study further provides better insight into the mechanism behind Ferric Uptake Regulator interactions with its DNA target. Finally, the mechanism behind mRNA cleavage of the marine-derived enzyme Oligoribonuclease was revealed by activity studies and new structural insight of the protein molecule.
Veiledere:
Bedømmelseskomité:
Leder av disputasen: Professor Camilla Brekke, prodekan for forskning, Fakultet for naturvitenskap og teknologi, UiT
Prøveforelesning:
6. februar klokken 14.15 samme sted. Tittel på prøveforelesningen er:
«Ribozymes: structure, function, and therapeutic applications»