Table 1.
Summary of MCR crystal structures with associated PTM content.
| MCR crystal structure | PDB | N1-methyl-His | S-methyl-Cys | 2-(S)-methyl-Gln | 5-(S)-methyl-Arg | Thioglycine | Didehydro-Asp | 6-hydroxy-Trp | 7-hydroxy-Trp | 3-methyl-Ile | N2-methyl-His | S-oxy-Met |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Methanothermobacter marburgensis MCR I (Ermler et al., 1997; Wagner et al., 2016) | 5A0Y | + | + | + | + | + | + | − | − | − | − | − |
| Methanothermobacter marburgensis MCR II (Wagner et al., 2016) | 5A8R | + | + | + | + | + | + | − | − | − | − | − |
| Methanosarcina barkeri (Grabarse et al., 2000; Wagner et al., 2016) | 1E6Y | + | + | − | + | + | + | − | − | − | − | − |
| Methanosarcina acetivorans (Nayak et al., 2020) | + | + | − | + | + | + | − | − | − | − | − | |
| Methanopyrus kandleri (Grabarse et al., 2000; Kahnt et al., 2007) | 1E6V | + | − | + | + | + | − | − | − | − | − | − |
| Methanotorris formicicus (Wagner et al., 2017) | 5N2A | + | − | + | + | + | − | + | − | − | − | − |
| Methanothermobacter wolfeii (Wagner et al., 2016) | 5A8K | + | + | + | + | + | − | − | − | − | − | − |
| Methanothermococcus thermolithotrophicus (Wagner et al., 2017) | 5N1Q | + | − | + | + | + | − | − | − | − | − | − |
| Methermicoccus shengliensis (Kurth et al., 2021b) | 7NKG | + | − | − | + | + | − | − | − | − | − | − |
| ANME–1 from Black Sea mats (Shima et al., 2012) | 3SQG | + | +/−a | − | − | +/−a | − | − | + | − | − | + |
| Ca. Ethanoperedens thermophilum (Hahn et al., 2021) | 7B1S | + | + | + | + | + | − | − | − | + | + | − |
a
Early mass spectrometry data indicated that ANME-1 MCR lacked the S-methylcysteine as well as thioglycine (Kahnt et al., 2007), while the ANME-1 MCR crystal structure showed the thioglycine was present (Shima et al., 2012). However, the sample used for crystallization represented a mixed population where 30% contained thioglycine but not S-methylcysteine, while the majority (70%) contained S-methylcysteine but not thioglycine and did not result in crystal formation (Shima et al., 2012).
(+) indicates PTM is present and (−) indicates PTM is absent.