Characterization of the charge-charge interaction in mediating Chemokine PF4 tetramer formation

• Main Authors: Ya, Pan Chen, 潘辰亞
• Other Authors: 蘇士哲
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/11312071171258818208

碩士 === 國立清華大學 === 生物資訊與結構生物研究所 === 103 === Chemokine is a protein that is described for their abilities to recruit leukocytes and affect inflammatory. Chemokines has different oligomerization states to execute different bio-functions. Platelet factor-4 (PF4 or named as CXCL4) is the first chemokine described as anti-angiogenesis chemokine. Tetrameric PF4 has high affinity to glycosaminoglycans (GAGs) while monomeric PF4 has been speculated to bind with G-protein coupled receptor (GPCR) to trigger the downstream signal. For execute the bio-functions, PF4 oligomers should be precisely controlled and the factor in mediating PF4 assembling is worthwhile for studying. There is a reported relationship between charge-charge interaction and oligomerization states of chemokines. By changing the content of salt and pH value, PF4 has distinct salt-bridge interaction and protonation status of residues. The effects modulate the transition of tetramer, dimer and monomer. We made point mutations on the interface to disrupt the intrinsic interaction. NMR HSQC method reported PF4 basic structural property and oligomerization states. We also tested the experiments of heparin binding, size-exclusion chromatography and analytical ultracentrifuge to classify the biophysical properties. We reveal that charge-charge and salt-bridge interaction actually dominantly regulates the oligomerization states, as the PF4 mutations with influence in structure and oligomerization states. In the future, we could do deeper research on the factors of oligomerization states by other point mutations. The effort would contribute in the preparation of pure oligomerization states of PF4.