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Asymmetric Configurations in a Reengineered Homodimer Reveal Multiple Subunit Communication Pathways in Protein Allostery
Author(s) -
Lanfranco Maria Fe,
Garate Fernanda,
Engdahl Ashton,
Maillard Rodrigo
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.118.4
Subject(s) - allosteric regulation , cooperativity , protein subunit , cooperative binding , dimer , mutant , chemistry , mutation , ligand (biochemistry) , biophysics , biology , receptor , biochemistry , binding site , gene , organic chemistry
Many allosteric proteins form homo‐oligomeric complexes to regulate a biological function. In homo‐oligomers, subunits establish communication pathways that are modulated by external stimuli like ligand binding. A challenge for dissecting the communication mechanisms in homo‐oligomers is identifying intermediate liganded states, which are typically transiently populated. However, their identities provide the most mechanistic information on how ligand‐induced signals propagate from bound to empty subunits. Here, we dissected the directionality and magnitude of subunit communication in a reengineered, single‐chain version of the homodimeric transcription factor cAMP Receptor Protein (CRP SC ). By combining wild‐type and mutant subunits in various asymmetric configurations, we revealed a linear relationship between the magnitude of cooperative effects and the number of mutant subunits. We found that a single mutation is sufficient to change the global allosteric behavior of the dimer even when one subunit remains wild‐type. Dimers harboring two mutations with opposite cooperative effects had different allosteric properties depending on the arrangement of the mutations. When the two mutations were placed in the same subunit, the resulting cooperativity was neutral. In contrast, when placed in different subunits, the observed cooperativity was dominated by the mutation with strongest effects over cAMP affinity relative to wild‐type. These results highlight the distinct roles of intrasubunit interactions and intersubunit communication in allostery. Finally, dimers bound to either one or two cAMP molecules had similar DNA affinities, indicating that both asymmetric and symmetric liganded states activate DNA interactions. These studies have revealed the multiple communication pathways that homo‐oligomers employ to transduce signals. Support or Funding Information This work was supported with startup funds from Georgetown University. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .