A novel structural unit in the N-terminal region of filamins.
Immunoglobulin-like (Ig) domains are a widely expanded superfamily that act as interaction motifs or as structural spacers in multidomain proteins. Vertebrate filamins (FLNs), which are multifunctional actin-binding proteins, consist of 24 Ig domains. We have recently discovered that in the C-terminal rod 2 region of FLN, Ig domains interact with each other forming functional domain pairs, where the interaction with signaling and transmembrane proteins is mechanically regulated by weak actomyosin contraction forces. Here, we investigated if there are similar inter-domain interactions around domain 4 in the N-terminal rod 1 region of FLN. Protein crystal structures revealed a new type of domain organization between domains 3, 4, and 5. In this module, domains 4 and 5 interact rather tightly, whereas domain 3 has a partially flexible interface with domain 4. NMR peptide titration experiments showed that within the three-domain module, domain 4 is capable for interaction with a peptide derived from platelet glycoprotein Ib. Crystal structures of FLN domains 4 and 5 in complex with the peptide revealed a typical β sheet augmentation interaction observed for many FLN ligands. Domain 5 was found to stabilize domain 4, and this could provide a mechanism for the regulation of domain 4 interactions.
From the Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, P. O. Box 35, Survontie 9, 40014 Jyväskylä.
Ritika
R
Sethi
Jonne
J
Seppälä
Helena
H
Tossavainen
Mikko
M
Ylilauri
Salla
S
Ruskamo
Olli T
OT
Pentikäinen
Ulla
U
Pentikäinen
Perttu
P
Permi
Jari
J
Ylänne
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D064448:Filamins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
D064448:Filamins
Cell Signaling; Filamin; Immunogloblulin-like Domain; Microfilaments; NMR; Platelet Glycoprotein Ib; Protein-Protein Interactions; Structural Biology; X-ray Crystallography; X-ray Scattering