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Smaldone G, Ruggiero A, Balasco N, Abuhammad A, Autiero I, Caruso D, Esposito D, Ferraro G, Gelardi ELM, Moreira M, Quareshy M, Romano M, Saaret A, Selvam I, Squeglia F, Troisi R, Kroon-Batenburg LMJ, Esposito L, Berisio R, Vitagliano L. The non-swapped monomeric structure of the arginine-binding protein from Thermotoga maritima. Acta Crystallogr F Struct Biol Commun 2019; 75:707-713. [PMID: 31702584 DOI: 10.1107/s2053230x1901464x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 10/29/2019] [Indexed: 01/07/2023] Open
Abstract
Domain swapping is a widespread oligomerization process that is observed in a large variety of protein families. In the large superfamily of substrate-binding proteins, non-monomeric members have rarely been reported. The arginine-binding protein from Thermotoga maritima (TmArgBP), a protein endowed with a number of unusual properties, presents a domain-swapped structure in its dimeric native state in which the two polypeptide chains mutually exchange their C-terminal helices. It has previously been shown that mutations in the region connecting the last two helices of the TmArgBP structure lead to the formation of a variety of oligomeric states (monomers, dimers, trimers and larger aggregates). With the aim of defining the structural determinants of domain swapping in TmArgBP, the monomeric form of the P235GK mutant has been structurally characterized. Analysis of this arginine-bound structure indicates that it consists of a closed monomer with its C-terminal helix folded against the rest of the protein, as typically observed for substrate-binding proteins. Notably, the two terminal helices are joined by a single nonhelical residue (Gly235). Collectively, the present findings indicate that extending the hinge region and conferring it with more conformational freedom makes the formation of a closed TmArgBP monomer possible. On the other hand, the short connection between the helices may explain the tendency of the protein to also adopt alternative oligomeric states (dimers, trimers and larger aggregates). The data reported here highlight the importance of evolutionary control to avoid the uncontrolled formation of heterogeneous and potentially harmful oligomeric species through domain swapping.
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Affiliation(s)
| | - Alessia Ruggiero
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Nicole Balasco
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Areej Abuhammad
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Ida Autiero
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Daniela Caruso
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Davide Esposito
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Giarita Ferraro
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | | | - Miguel Moreira
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Mussa Quareshy
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Maria Romano
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Annica Saaret
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Irwin Selvam
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Flavia Squeglia
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Romualdo Troisi
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | | | - Luciana Esposito
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Rita Berisio
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
| | - Luigi Vitagliano
- AIC School Crystallographic Information Fiesta 2019, Naples, Italy
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