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. 2018 Sep 20;7(10):124. doi: 10.3390/antiox7100124

Figure 4.

Figure 4

Archaeal MSRA/B stand-alone and fusion protein homologs. (A) Protein domain architecture of archaeal MSRA/B homologs. The black box indicates the coiled coil domain that links the ThyX and MSRB domains. (B) Archaeal AANH-MSRB (e.g., Uniprot: A0A2D6JNB0) has a predicted structural fold related to the adenylation (AANH) domain of tRNA sulfurtransferases such as Thermotoga maritima ThiI (Protein Data Bank or PDB: 4KR7) and the MSRB domain of Streptococcus pneumoniae MSRAB (PDB:3E0M). The active site cysteine nucleophiles of the AANH (Cys*162) and MsrB (CysA389) domains as well as the resolving Cys residue of MsrB (CysR334) are conserved. The N-terminal ferredoxin-like domain (NFLD) and RNA binding THUMP (thiouridine synthases, RNA methylases and pseudouridine synthases) domain of ThiI are not conserved. (C) Archaeal aThyX-MSRB (Uniprot A0A075GM99) has a predicted structural fold related to Thermotoga maritima flavin-dependent thymidylate synthase (ThyX, PDB: 1O26) and the Zn2+-binding MSRB of Methanothermobacter thermautotrophicus (MTH711, PDB: 2K8D). The ThyX flavin-binding site and MSRB CysA nucleophile and CysS Zn2+ coordinating residues are conserved; however, the serine residue (S88*) required for ThyX catalytic activity is not conserved in the aThyX-MSRB. TRX: thioredoxin domain; GRX: glutaredoxin domain.