Mabinlin

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Mabinlin 1
Identifiers
Symbol2SS1_CAPMA
UniProtP80351
Mabinlin 2
Identifiers
Symbol2SS2_CAPMA
PDB2DS2
UniProtP30233
Mabinlin 3
Identifiers
Symbol2SS3_CAPMA
UniProtP80352
Mabinlin 4
Identifiers
Symbol2SS4_CAPMA
UniProtP80353

Four homologues sweet-tasting proteins mabinlin were extracted from the seed of Mabinlang (Capparis masaikai Levl.), a Chinese plant growing in Yunnan province. Mabinlin-2 was first isolated in 1983[1] and characterised in 1993,[2] it is the most studied protein. The 3 other variants of mabinlin-1, -3 and -4 were discovered and characterised in 1994.[3]

Protein structure

The 4 mabinlins are very similar in their Amino acids sequences (see below).

Chain A
M-1: EPLCRRQFQQ HQHLRACQRY IRRRAQRGGL VD
M-2: QLWRCQRQFL QHQRLRACQR FIHRRAQFGG QPD
M-3: EPLCRRQFQQ HQHLRACQRY LRRRAQRGGL AD
M-4: EPLCRRQFQQ HQHLRACQRY LRRRAQRG

Chain B
M-1: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRQLFR AARNLPNICK IPAVGRCQFT RW
M-2: QPRRPALRQC CNQLRQVDRP CVCPVLRQAA QQVLQRQIIQ GPQQLRRLFD AARNLPNICN IPNIGACPFR AW
M-3: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW
M-4: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW
Amino acids sequence of the sweet-tasting proteins Mabinlins homologues adapted from Swiss-Prot biological database of protein.[4][5][6][7]

The molecular weights of Mabinlin-1, Mabinlin-3 and Mabinlin-4 are 12.3 kDa. 12.3 kDa. and 11.9 kDa respectively.[3]
With a weight of 10.4kDa, mabinlin-2 is lighter than mabinlin-1. It is a hetero dimmer consisting of two different chains A and B. The A chain is composed of 33 amino acid residues and the B chain is composed of 72 amino acid residues. The B chain contains two intramolecular disulphide bonds and is connected to the A chain through two intermolecular disulphide bridges.[2][8]
Mabinlin-2 is the sweet-tasting protein with the highest known thermostablility,[9] which is due to the presence of the four disulfide bridges.[10] It has been suggested also that the difference in the heat stability of the different mabinlin homologues is due to the presence of an arginine residue (heat-stable homologue) or a glutamine (heat-unstable homologue) at position 47 in the B-chain.[3]

Sweetness properties

Mabinlins sweetness were estimated to be about 100-400 times that of sucrose on weight basis, which make them less sweet than thaumatin (3000 times) but elicit a similar sweetness profile.
The sweetness of mabinlin-2 is unchanged after 48 hours incubation at boiling point.[2]
Mabinlin-3 and -4 sweetness stayed unchanged after 1 hour at 80°C, while mabinlin-1 loses sweetness after 1 hour at the same condition.[3][11]


As a sweetener

Mabinlins, as proteins, are readily soluble in water and found to be highly sweet, however mabilin-2 with its high heat stability as the best chance to be used as a sweetener.
Last decade, researches undertake to produce industrially mabinlin-2 through expression in micro-organisms and synthesis are more or less successful. The sweet-tasting protein has been successfully synthesised by a stepwise solid-phase method in 1998, however the synthetic protein had an astringent-sweet taste.[8]
Mabinlin-2 has been expressed in transgenic potato tubers, but no explicit results have been reported yet. [12]
However, patents to protect production of recombinant mabinlin by cloning and DNA sequencing has been issued. [13]

References

  1. Z Hu and M He. Studies on mabinlin, a sweet protein from the seeds of Capparis masaikai levl. I. extraction, purification and certain characteristics. Acta Botan. Yunnan. 1983, 5, 207–212.
  2. 2.0 2.1 2.2 X Liu, S Maeda, Z Hu, T Aiuchi, K Nakaya, Y Kurihara. Purification, complete amino acid sequence and structural characterization of the heat-stable sweet protein, mabinlin II. Eur J Biochem 1993. 211(1–2):281-7.
  3. 3.0 3.1 3.2 3.3 S Nirasawa, T Nishino, M Katahira, S Uesugi, Z Hu, Y Kurihara. Structures of heat-stable and unstable homologues of the sweet protein mabinlin. Eur J Biochem 1994, 223(3):989-95.
  4. UniProtKB/Swiss-Prot database entry for 2SS1_CAPMA (P80351).
  5. UniProtKB/Swiss-Prot database entry for 2SS2_CAPMA (P30233).
  6. UniProtKB/Swiss-Prot database entry for 2SS3_CAPMA (P80352).
  7. UniProtKB/Swiss-Prot database entry for 2SS4_CAPMA (P80353).
  8. 8.0 8.1 Kohmura M, Ariyoshi Y: Chemical synthesis and characterization of the sweet protein mabinlin II. Biopolymers 1998, 46(4):215-23.
  9. RJ Guan, JM Zheng, Z Hu, DC Wang. Crystallization and preliminary X-ray analysis of the thermostable sweet protein mabinlin II. Acta Crystallogr D Biol Crystallogr 2000, 56(Pt 7):918-9.
  10. S Nirasawa, X Liu, T Nishino, Y Kurihara. Disulfide bridge structure of the heat-stable sweet protein mabinlin II. Biochim Biophys Acta 1993, 1202(2):277-80.
  11. Y Kurihara and S Nirasawa. Structures and activities of sweetness-inducing substances (miraculin, curculin, strogin) and the heat-stable sweet protein, mabinlin. Foods and Food Ingredients Journal of Japan 1997.174:67-74.
  12. LW Xiong and S Sun. Molecular cloning and transgenic expression of the sweet protein mabinlin in potato tubers. Plant Physiology 1996, 111, 147.
  13. S Sun, L Xiong, Z Hu and H Chen. Recombinant Sweet protein Mabinlin. US PAT No. 6,051,758

See also



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