Table 5 Difference between two well characterised known groups of methanobactins
From: Metal(loid) speciation and transformation by aerobic methanotrophs
Particulars | Group 1 methanobactin (e.g. Ms. trichosporium OB3b) | Group 2 methanobactin (e.g. Methylocystis strain SB2) |
|---|---|---|
Molecular weight (Da.) | 1154.26 | 851.20 |
Structural difference | Two oxazolone rings (UV-vis spectra: Ring A ~ 394nm and B ~ 342nm) | One oxazolone ring (UV-vis spectra: Ring B~ 338nm) and Imidazolone (UV-vis spectra: Ring A ~ 387nm) |
Partial amino-acids associated with Ring-A | Leucine | Arginine |
Partial amino-acids associated with Ring-B | Proline | Threonine |
Amino acids | Gly1, Ser2, Cys3, Tyr4, Ser5, Cys6 and Met7 (Gly1 – Downfield shift at 9.28ppm) | Ala1, Ser2, Ala3, Ala4 (Ala1 – Downfield shift at 11.7 and 145 ppm) |
Copper affinity | 1018–1050 M-1 | 1026 M-1 |
Copper binding Ring-A | 640 S-1 | Not available |
Copper co-ordination rate with Ring-B | 121 S-1 | >2000 S-1 |
Structure modification | Pyramid-like structure | Hairpin-like structure |
Stability | Both rings hydrolysed within 2–5 days under acidic condition | Ring B (i.e. Oxa) is susceptible to hydrolysis (200 min) and Ring-A more resistance |
Disulphide bond | Found | Not found |
Sulphate group | Not found | Found |