Mabinlin

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Also known as: Mabinlin I, MAB I
'Mabinlin 1'
Identifiers
Symbol 2SS1_CAPMA
UniProt P80351
Other data
Also known as: Mabinlin II, MAB II
'Mabinlin 2'
Identifiers
Symbol 2SS2_CAPMA
PDB 2DS2
UniProt P30233
Other data
Also known as: Mabinlin III, MAB III
'Mabinlin 3'
Identifiers
Symbol 2SS3_CAPMA
UniProt P80352
Other data
Also known as: Mabinlin IV, MAB IV
'Mabinlin 4'
Identifiers
Symbol 2SS4_CAPMA
UniProt P80353
Other data

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

Contents

[edit] Protein structures

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 acid sequence of Mabinlins homologues are 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 molecular weight of 10.4kDa, mabinlin-2 is lighter than mabinlin-1. It is a heterodimer 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 disulfide bonds and is connected to the A chain through two intermolecular disulfide bridges.[2][8]

Mabinlin-2 is the sweet-tasting protein with the highest known thermostability,[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]

[edit] Sweetness properties

Mabinlins sweetness were estimated to be about 100-400 times that of sucrose on weight basis,[2][3] which make them less sweet than thaumatin (3000 times) but elicit a similar sweetness profile.[11]

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][12]

[edit] As a sweetener

Mabinlins, as proteins, are readily soluble in water and found to be highly sweet, however mabinlin-2 with its high heat stability has the best chance to be used as a sweetener.

During the past decade, attempts have been made to produce mabinlin-2 industrially. 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.[13] However, patents to protect production of recombinant mabinlin by cloning and DNA sequencing have been issued.[14]

[edit] 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. ^ a b c d 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. ^ a b c d e 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. ^ a b 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. 1992. Characteristics of antisweet substances, sweet proteins, and sweetness-inducing proteins. Crit. Rev. Food Sci. Nutr. 32:231-252.
  12. ^ 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.
  13. ^ LW Xiong and S Sun. Molecular cloning and transgenic expression of the sweet protein mabinlin in potato tubers. Plant Physiology 1996, 111, 147.
  14. ^ S Sun, L Xiong, Z Hu and H Chen. Recombinant Sweet protein Mabinlin. US PAT No. 6,051,758 

[edit] See also

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