Estimation of interdomain flexibility of N-terminus of factor H using residual dipolar couplings

Characterization of segmental flexibility is needed to understand the biological mechanisms of the very large category of functionally diverse proteins, exemplified by the regulators of complement activation, that consist of numerous compact modules or domains linked by short, potentially flexible, sequences of amino acid residues. The use of NMR-derived residual dipolar couplings (RDCs), in magnetically aligned media, to evaluate interdomain motion is established but only for two-domain proteins. We focused on the three N-terminal domains (called CCPs or SCRs) of the important complement regulator, human factor H (i.e. FH1-3). These domains cooperate to facilitate cleavage of the key complement activation-specific protein fragment, C3b, forming iC3b that no longer participates in the complement cascade. We refined a three-dimensional solution structure of recombinant FH1-3 based on nuclear Overhauser effects and RDCs. We then employed a rudimentary series of RDC datasets, collected in media containing magnetically aligned bicelles (disk-like particles formed from phospholipids) under three different conditions, to estimate interdomain motions. This circumvents a requirement of previous approaches for technically difficult collection of five independent RDC datasets. More than 80% of conformers of this predominantly extended three-domain molecule exhibit flexions of < 40 °. Such segmental flexibility (together with the local dynamics of the hypervariable loop within domain 3), could facilitate recognition of C3b via initial anchoring and eventual reorganization of modules to the conformation captured in the previously solved crystal structure of a C3b:FH1-4 complex

Opini penonton remaja perempuan di Surabaya mengenai tayangan sinetron ganteng-ganteng serigala di stasiun televisi SCTV

Penelitian ini berfokus pada bagaimana opini dari penonton remaja perempuan di Surabaya mengenai tayangan sinetron ganteng-ganteng serigala. Teori utama yang terdapat pada penelitian ini ialah teori SOR (Stimulus-Organism-Response) dimana stimulus dalam penelitian ini ialah sinetron ganteng-ganteng serigala, organism adalah remaja perempuan di Surabaya yang menonton sinetron ganteng-ganteng serigala, dan response adalah opini dari penonton remaja perempuan di Surabaya mengenai tayangan sinetron ganteng-ganteng serigala di stasiun televisi SCTV. Opini memiliki tiga indikator, yaitu beliefe, attitude, dan perception pada penonton remaja perempuan di Surabaya setelah menonton sinetron ganteng-ganteng serigala di stasiun televisi SCTV. Peneliti menggunakan metode survei untuk pengamatan atau penyelidikan secara kritis untuk mendapatkan keterangan yang tepat dari penonton remaja perempuan di Surabaya mengenai sinetron ganteng-ganteng serigala di stasiun televisi SCTV. Informasi yang dikumpulkan dalam penelitian ini dengan menggunakan kuesioner kepada penonton remaja perempuan di Surabaya. Hasil dari penelitian yang berjudul opini penonton remaja di Surabaya mengenai tayangan pada sinetron ganteng-ganteng serigala eli stasiun televisi SCTV yaitu remaja perempuan di Surabaya merniliki opini positif

Determining Interdomain Structure and Dynamics of a Retroviral Capsid Protein in the Presence of Oligomerization: Implication for Structural Transition in Capsid Assembly

Capsid (CA) proteins from all retroviruses, including HIV-1, are structurally homologous dual-domain helical proteins. They form a capsid lattice composed of unitary symmetric CA hexamers. X-ray crystallography has shown that within each hexamer a monomeric CA adopts a single conformation, where most helices are parallel to the symmetry axis. In solution, large differences in averaged NMR spin relaxation rates for the two domains were observed, suggesting they are dynamically independent. One relevant question for the capsid assembly remains: whether the interdomain conformer within a hexamer unit needs to be induced or pre-exists within the conformational space of a monomeric CA. The latter seems more consistent with the relaxation data. However, possible CA protein oligomerization and the structure of each domain will affect relaxation measurements and data interpretation. This study, using CA proteins from equine infectious anemia virus (EIAV) as an example, demonstrates a linear extrapolation approach to obtain backbone ¹⁵N spin relaxation time ratios <i>T</i>₁/<i>T</i>₂ for a monomeric EIAV-CA in the presence of oligomerization equilibrium. The interdomain motion turns out to be limited. The large difference in the domain averaged ⟨<i>T</i>₁/<i>T</i>₂⟩ for a CA monomer is a consequence of the orthogonal distributions of helices in the two domains. The new monomeric interdomain conformation in solution is significantly different from that in CA hexamer. Therefore, if capsid assembly follows a nucleation–propagation process, the interdomain conformational change might be a key step during the nucleation, as the configuration in hexagonal assembly is never formed by diffusion of its two domains in solution