Structure/Function Analysis of Protein–Protein Interactions Developed by the Yeast Pih1 Platform Protein and Its Partners in Box C/D snoRNP Assembly

ABSTRACT Poxvirus virions, whose outer membrane surrounds two lateral bodies and a core, contain at least 70 different proteins. The F18 phosphoprotein is one of the most abundant core components and is essential for the assembly of mature virions. We report here the results of a structure/function analysis in which the role of conserved cysteine residues, clusters of charged amino acids and clusters of hydrophobic/aromatic amino acids have been assessed. Taking advantage of a recombinant virus in which F18 expression is IPTG (isopropyl-β-d-thiogalactopyranoside) dependent, we developed a transient complementation assay to evaluate the ability of mutant alleles of F18 to support virion morphogenesis and/or to restore the production of infectious virus. We have also examined protein-protein interactions, comparing the ability of mutant and WT F18 proteins to interact with WT F18 and to interact with the viral A30 protein, another essential core component. We show that F18 associates with an A30-containing multiprotein complex in vivo in a manner that depends upon clusters of hydrophobic/aromatic residues in the N′ terminus of the F18 protein but that it is not required for the assembly of this complex. Finally, we confirmed that two PSSP motifs within F18 are the sites of phosphorylation by cellular proline-directed kinases in vitro and in vivo. Mutation of both of these phosphorylation sites has no apparent impact on virion morphogenesis but leads to the assembly of virions with significantly reduced infectivity.

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Structure/Function Analysis of Protein-Protein Interactions and Role of Dynamic Motions in Mercuric Ion Reductase

10.2172/840156 ◽

2005 ◽

Author(s):

Susan M. Miller

Keyword(s):

Structure Function ◽

Protein Interactions ◽

Function Analysis ◽

Protein Protein Interactions ◽

Mercuric Ion

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The toxofilin–actin–PP2C complex of Toxoplasma: identification of interacting domains

Biochemical Journal ◽

10.1042/bj20061324 ◽

2007 ◽

Vol 401 (3) ◽

pp. 711-719 ◽

Cited By ~ 13

Author(s):

Gaelle Jan ◽

Violaine Delorme ◽

Violaine David ◽

Celine Revenu ◽

Angelita Rebollo ◽

...

Keyword(s):

Protein Interactions ◽

Actin Filaments ◽

Function Analysis ◽

Protozoan Parasite ◽

Actin Binding ◽

Protein Protein Interactions ◽

The Third ◽

Parasite Motility

Toxofilin is a 27 kDa protein isolated from the human protozoan parasite Toxoplasma gondii, which causes toxoplasmosis. Toxofilin binds to G-actin, and in vitro studies have shown that it controls elongation of actin filaments by sequestering actin monomers. Toxofilin affinity for G-actin is controlled by the phosphorylation status of its Ser53, which depends on the activities of a casein kinase II and a type 2C serine/threonine phosphatase (PP2C). To get insights into the functional properties of toxofilin, we undertook a structure–function analysis of the protein using a combination of biochemical techniques. We identified a domain that was sufficient to sequester G-actin and that contains three peptide sequences selectively binding to G-actin. Two of these sequences are similar to sequences present in several G- and F-actin-binding proteins, while the third appears to be specific to toxofilin. Additionally, we identified two toxofilin domains that interact with PP2C, one of which contains the Ser53 substrate. In addition to characterizing the interacting domains of toxofilin with its partners, the present study also provides information on an in vivo-based approach to selectively and competitively disrupt the protein–protein interactions that are important to parasite motility.

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Understanding structure, function, and evolution of protein-protein interactions by computational modeling and analysis

10.32469/10355/37826 ◽

2013 ◽

Author(s):

Nan Zhao

Keyword(s):

Computational Modeling ◽

Structure Function ◽

Protein Interactions ◽

Protein Protein Interactions ◽

Modeling And Analysis

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Bacterioferritin: Structure Function and Protein–Protein Interactions

Handbook of Porphyrin Science - Handbook of Porphyrin Science (Volume 30) ◽

10.1142/9789814407755_0041 ◽

2013 ◽

pp. 135-178 ◽

Cited By ~ 2

Author(s):

Mario Rivera

Keyword(s):

Structure Function ◽

Protein Interactions ◽

Protein Protein Interactions

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Structure, function and inhibition of critical protein–protein interactions involving mixed lineage leukemia 1 and its fusion oncoproteins

Journal of Hematology & Oncology ◽

10.1186/s13045-021-01057-7 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Xin Li ◽

Yongcheng Song

Keyword(s):

Structure Function ◽

Protein Interactions ◽

Hox Genes ◽

Mixed Lineage Leukemia ◽

Fusion Partner ◽

Wild Type ◽

Protein Protein Interactions ◽

Leukemic Transformation ◽

Chromosome Translocations ◽

Partner Proteins

AbstractMixed lineage leukemia 1 (MLL1, also known as MLL or KMT2A) is an important transcription factor and histone-H3 lysine-4 (H3K4) methyltransferase. It is a master regulator for transcription of important genes (e.g., Hox genes) for embryonic development and hematopoiesis. However, it is largely dispensable in matured cells. Dysregulation of MLL1 leads to overexpression of certain Hox genes and eventually leukemia initiation. Chromosome translocations involving MLL1 cause ~ 75% of acute leukemia in infants and 5–10% in children and adults with a poor prognosis. Targeted therapeutics against oncogenic fusion MLL1 (onco-MLL1) are therefore needed. Onco-MLL1 consists of the N-terminal DNA-interacting domains of MLL1 fused with one of > 70 fusion partners, among which transcription cofactors AF4, AF9 and its paralog ENL, and ELL are the most frequent. Wild-type (WT)- and onco-MLL1 involve numerous protein–protein interactions (PPI), which play critical roles in regulating gene expression in normal physiology and leukemia. Moreover, WT-MLL1 has been found to be essential for MLL1-rearranged (MLL1-r) leukemia. Rigorous studies of such PPIs have been performed and much progress has been achieved in understanding their structures, structure–function relationships and the mechanisms for activating gene transcription as well as leukemic transformation. Inhibition of several critical PPIs by peptides, peptidomimetic or small-molecule compounds has been explored as a therapeutic approach for MLL1-r leukemia. This review summarizes the biological functions, biochemistry, structure and inhibition of the critical PPIs involving MLL1 and its fusion partner proteins. In addition, challenges and perspectives of drug discovery targeting these PPIs for the treatment of MLL1-r leukemia are discussed.

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