Chemokines tetramers, structures

Previously, the structure of MGP-1 /GGL2 was solved by NMR and subsequently by X-ray crystallography using the NMR structure as a starting model for molecular replacement (Lubkowski et al, 1997). As described in Section II.B, the solution structure revealed a dimer similar to dimerization motifs observed for other GC chemokines. In the case of the X-ray structure, two different crystal forms were isolated from the same droplet. One form contained a dimer similar to the solution structure (Fig. 2B), while the other form contained a tetramer as shown in Fig. 8. In the tetramer, there is a primary CC dimer interface that consists of the... 

Interferon-7-inducible protein 10 kDa (IP-IO/GXGLIO) is a chemokine that in solution, exists in equilibrium between monomer and dimer. A solution structure of a monomeric variant has been solved by NMR (Booth et al, 2002). However, like MGP-1, it has also been crystallized in different space groups, revealing tetrameric oligomerization states (Swaminathan et al, 2003). One of the forms is similar to the PF4 and MGP-1 tetramers. The other two tetramers form a novel twelve-stranded /3-sheet containing structure (Fig. 9), which the authors postulate could represent structures induced by binding of different GAGs. 

Fig. 9. Ribbon structures of the three IP-IO/CXCLIO tetramers. Two orthogonal views are shovm for each. The M-form is similar to the PF4/CXCL8 and MCP-1/CCL2 structures that contain elements of CXC and CC dimers. The T and H forms contain a novel 12-stranded / -sheet. Reprinted from Structure with copyright permission from Elsevier. Swaminathan, G. et al. (2003). Crystal structures of oligomeric forms of the IP-lO/CXCLlO chemokine. Structure 11, 521-532. (See Color Insert.)...

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