DYNAMIC STRUCTURES OF GRANULOCYTE-COLONY-STIMULATING FACTOR PROTEINS STUDIED BY NORMAL-MODE ANALYSIS - 2 DOMAIN-TYPE MOTIONS IN LOW-FREQUENCY MODES

In this study, granulocyte colony-stimulating factor (GCSF) proteins m ere chosen as subjects for normal mode analysis. As helical cytokines with a four helix bundled type topology, they were classified into lon g chain and short chain groups by Sprang and Bazan, Normal mode calcul ations were also carried out with leukemia inhibitory factor (LIF), in terleukin-6 (IL-6), and growth hormone (GH) as members of the long cha in group and GCSF and IL-2 and IL-4 as members of the short chain grou p. For the GCSF families it was found that the fluctuations in the hel ical region are smaller than in the loop region, and it is clear that on the whole the smaller fluctuation residues belong to a large hydrop hobic core region. Thus, it can be imagined how the receptor binding s ites approach the receptor within the normal time-scale of pico second s. In addition, two similar domain-type motions in low frequency modes were found with proteins in the long chain group, although we never o bserved any sequence similarity in the two separate two-domain regions in each protein of the long chain group, On the other hand, these two domain-type motions were not clear in proteins of the short chain gro up.