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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
  1. Note: Da. daltons, UV ultraviolet, Gly glycine, Ser serine, Cys cystine, Tyr tyrosine, Met methionine, ppm parts per million