title: Structural and thermodynamic characterization of Nore1-SARAH: a small, helical module important in signal transduction networks.
abstract: Tumor suppressor Nore1, its acronym coming from novel Ras effector, is one of the 10 members of the Rassf (Ras association domain family) protein family that have been identified. It is expressed as two mRNA splice variants, Nore1A and a shorter isoform, Nore1B. It forms homo- and heterocomplexes through its C-terminal SARAH (Sav/Rassf/Hpo) domain. The oligomeric state of Nore1 and other SARAH domain-containing proteins is important for their cellular activities. However, there are few experimental data addressing the structural and biophysical characterization of these domains. In this study, we show that the recombinant SARAH domain of Nore1 crystallizes as an antiparallel homodimer with representative characteristics of coiled coils. As is typical for coiled coils, the SARAH domain shows a heptad register, yet the heptad register is interrupted by two stutters. The comparisons of the heptad register of Nore1-SARAH with the primary structure of Rassf1-4, Rassf6, MST1, MST2, and WW45 indicate that these proteins have a heptad register interrupted by two stutters, too. Moreover, on the basis of the structure of Nore1-SARAH, we also generate structural models for Rassf1 and Rassf3. These models indicate that Rassf1- and Rassf3-SARAH form structures very similar to that of Nore1-SARAH. In addition, we show that, as we have previously found for MST1, the SARAH domain of Nore1 undergoes association-dependent folding. Nevertheless, the Nore1 homodimer has a lower affinity and thermodynamic stability than the MST1 homodimer, while the monomer is slightly more stable. Our experimental results along with our theoretical considerations indicate that the SARAH domain is merely a dimerization domain and that the differences between the individual sequences lead to different stabilities and affinities that might have an important functional role.
authors: Ruhr University, Department of Physical Chemistry I, Protein Interactions, Universitätsstrasse 150, 44780 Bochum, Germany.
authors: Cihan
authors: C
authors: Makbul
authors: Diana
authors: D
authors: Constantinescu Aruxandei
authors: Eckhard
authors: E
authors: Hofmann
authors: Daniel
authors: D
authors: Schwarz
authors: Eva
authors: E
authors: Wolf
authors: Christian
authors: C
authors: Herrmann
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D019281:Dimerization; D017228:Hepatocyte Growth Factor / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D000090742:Serine-Threonine Kinase 3; D015398:Signal Transduction; D013816:Thermodynamics; D025521:Tumor Suppressor Proteins / Q000737:chemistry* / Q000378:metabolism; D000099317:Hippo Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins; D017228:Hepatocyte Growth Factor; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000090742:Serine-Threonine Kinase 3; D025521:Tumor Suppressor Proteins; C496882:RASSF1 protein, mouse; C455831:Rassf5 protein, mouse; C485935:Sav1 protein, mouse; C082332:macrophage stimulating protein; C490818:Stk3 protein, mouse; D000099317:Hippo Kinases