The Arp2y3 complex, a stable assembly of two actin-related proteins (Arp2 and Arp3) with five other subunits, caps the pointed end of actin filaments and nucleates actin polymerization with low efficiency. WASp and Scar are two similar proteins that bind the p21 subunit of the Arp2y3 complex, but their effect on the nucleation activity of the complex was not known. We report that full-length, r...

A three-dimensional structural model of an influenza virus ribonucleoprotein particle reconstituted in vivo from recombinant proteins and a model genomic vRNA has been generated by electron microscopy. It shows a circular shape and contains nine nucleoprotein monomers, two of which are connected with the polymerase complex. The nucleoprotein monomers show a curvature that may be responsible for...

The formation of homodimer complexes for interface stability, catalysis and regulation is intriguing. The mechanisms of homodimer complexations are even more interesting. Some homodimers form without intermediates (two-state (2S)) and others through the formation of stable intermediates (three-state (3S)). Here, we analyze 41 homodimer (25 2S and 16 3S) structures determined by X-ray crystallog...

The transition of the state of alamethicin from its inactive state to its active state of pore formation was measured as a function of the peptide concentration in three different membrane conditions. In each case the fraction of the alamethicin molecules occupying the active state, phi, showed a sigmoidal concentration dependence that is typical of the activities of antimicrobial peptides. Suc...

The two-dimensional monomer-monomer (AB) surface reaction model without diffusion is considered for infinitesimal, finite, and infinite reaction rates k. For equal reactant adsorption rates, in all cases, simulations reveal the same form of slow poisoning, associated with clustering of reactants. This behavior is also the same as that found in simulations of the two-dimensional voter model stud...

CD4 is a coreceptor for binding of T cells to APC and the primary receptor for HIV. The disulfide bond in the second extracellular domain (D2) of CD4 is reduced on the cell surface, which leads to formation of disulfide-linked homodimers. A large conformational change must take place in D2 to allow for formation of the disulfide-linked dimer. Domain swapping of D2 is the most likely candidate f...

Most well-known restriction endonucleases recognize palindromic DNA sequences and are classified as Type IIP. Due to the recognition and cleavage symmetry, Type IIP enzymes are usually found to act as homodimers in forming 2-fold symmetric enzyme-DNA complexes. Here we report an asymmetric complex of the Type IIP restriction enzyme MspI in complex with its cognate recognition sequence. Unlike a...