Doctoral defence in Biochemistry - Kristinn Ragnar Óskarsson

Kristinn Ragnar Óskarsson will defend his doctoral thesis in Biochemistry on October 2nd

The defence will take place in the Veröld, room 023 and starts at 13:00.
Live stream:

Dissertation title: Kinetic stability and temperature adaptation. Observations from a cold adapted subtilisin-like serine protease.

Dr. Jose Manuel Sanchez-Ruiz, Professor at the Faculty of Physical Chemistry, University of Granada, Spain.
Dr. Tony Collins, Assistant Professor at the CBMA, University of Minho, Portugal

Advisor: Dr. Magnús Már Kristjánsson, Professor at Faculty of Physical Sciences at the University of Iceland.

Doctoral committee:
Dr. Bjarni Ásgeirsson, Professor at the Faculty of Physical Sciences at the University of Iceland.
Dr. Elena Papaleo, Associate Professor at Copenhagen University.

Chair of Ceremony: Dr. Einar Örn Sveinbjörnsson, Professor and the Head of the Faculty of Physical Sciences, University of Iceland

In order to study temperature adaptation and kinetic stability we have utilized a research consisting of the kinetically stable VPR, a cold active subtilisin-like serine protease and its thermostable structural homolog AQUI.

The results discussed in this doctoral defence talk will be on the importance of calcium binding for protein stability, the effects of insertions of proline residues in loops and the role of a conserved N-terminal tryptophan residue for structure of these proteins. Furthermore, the importance of the N-terminal region for structural stability of the proteins will be discussed.

A model is proposed of a native structure that unfolds in a highly cooperative manner. This cooperativity can be disrupted, however, by modifying calcium binding of the protein or via mutations that affect how the N-terminus interacts with the rest of the protein. The N-terminus likely acts as a kinetic lock that infers stability to the rest of the structure through different interactions. Some of these interactions may be strengthened via proline residues, that seemingly act as anchor points that tend to maintain correct orientation between these parts of the protein as thermal energy is increased in the system.

Our results give a deeper insight into the nature of the kinetic stability, the importance of cooperativity during unfolding of kinetically stable proteases, synergy between distant parts of the protein through proline mutations and how different calcium binding sites have vastly differing roles.

About the doctoral candidate:

Kristinn Ragnar Óskarsson enrolled into biochemistry at the University of Iceland in the fall of 2010 and finished a BSc degree in 2013. That same year he started working towards a master’s degree in biochemistry, which he finished in spring 2015. He started his doctoral research during fall of 2015 under the supervision of Magnús Már Kristjánsson, Professor at Faculty of Physical Sciences.

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