{{infobox nonhuman protein | Name = '''Mabinlin 1''' | caption = Also known as: Mabinlin I, MAB I | image = | width = | HGNCid = | Symbol = 2SS1_CAPMA | AltSymbols = | EntrezGene = | OMIM = | RefSeq = | UniProt = P80351 | PDB = | ECnumber = | Chromosome = | Arm = | Band = | LocusSupplementaryData = }} {{infobox nonhuman protein | Name = '''Mabinlin 2''' | caption = Also known as: Mabinlin II, MAB II | image = Mabinlin II 2DS2.png | HGNCid = | Symbol = 2SS2_CAPMA | AltSymbols = | EntrezGene = | RefSeq = | UniProt = P30233 | PDB = 2DS2 }}
{{infobox nonhuman protein | Name = '''Mabinlin 3''' | caption = Also known as: Mabinlin III, MAB III | image = | width = | HGNCid = | Symbol = 2SS3_CAPMA | AltSymbols = | EntrezGene = | RefSeq = | UniProt = P80352 | PDB = }} {{infobox nonhuman protein | Name = '''Mabinlin 4''' | caption = Also known as: Mabinlin IV, MAB IV | image = | width = | HGNCid = | Symbol = 2SS4_CAPMA | AltSymbols = | EntrezGene = | RefSeq = | UniProt = P80353 | PDB = }} thumb|Stick structure of the amino acid residues in segment B54-B64 in Mabinlin II. Constructed in PyMOL (PDB 2DS2). '''Mabinlins''' are sweet-tasting proteins extracted from the seed of mabinlang (''Capparis masaikai Levl.''), a plant growing in Yunnan province of China. There are four homologues. Mabinlin-2 was first isolated in 1983<ref name="hu-1983">{{cite journal |vauthors=Hu Z, He M |title=Studies on mabinlin, a sweet protein from the seeds of Capparis masaikai levl. I. extraction, purification and certain characteristics |journal=Acta Botan. Yunnan. |issue=5 |pages=207–212 |year=1983}}</ref> and characterised in 1993,<ref name="liu-1993">{{cite journal | vauthors = Liu X, Maeda S, Hu Z, Aiuchi T, Nakaya K, Kurihara Y | title = Purification, complete amino acid sequence and structural characterization of the heat-stable sweet protein, mabinlin II | journal = European Journal of Biochemistry | volume = 211 | issue = 1–2 | pages = 281–7 | date = January 1993 | pmid = 8425538 | doi = 10.1111/j.1432-1033.1993.tb19896.x }}</ref> and is the most extensively studied of the four. The other variants of mabinlin-1, -3 and -4 were discovered and characterised in 1994.<ref name="nirasawa-1994">{{cite journal | vauthors = Nirasawa S, Nishino T, Katahira M, Uesugi S, Hu Z, Kurihara Y | title = Structures of heat-stable and unstable homologues of the sweet protein mabinlin. The difference in the heat stability is due to replacement of a single amino acid residue | journal = European Journal of Biochemistry | volume = 223 | issue = 3 | pages = 989–95 | date = August 1994 | pmid = 8055976 | doi = 10.1111/j.1432-1033.1994.tb19077.x | doi-access = free }}</ref>
== Protein structures == The 4 mabinlins are very similar in their amino acids sequences (see below).
<blockquote> '''''Chain A'''''<br /> '''M-1:''' {{mono|EPLCRRQFQQ HQHLRACQRY IRRRAQRGGL VD}}<br /> '''M-2:''' {{mono|QLWRCQRQFL QHQRLRACQR FIHRRAQFGG QPD}}<br /> '''M-3:''' {{mono|EPLCRRQFQQ HQHLRACQRY LRRRAQRGGL AD}}<br /> '''M-4:''' {{mono|EPLCRRQFQQ HQHLRACQRY LRRRAQRG}}<br /><br /> '''''Chain B'''''<br /> '''M-1:''' {{mono|EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRQLFR AARNLPNICK IPAVGRCQFT RW}}<br /> '''M-2:''' {{mono|QPRRPALRQC CNQLRQVDRP CVCPVLRQAA QQVLQRQIIQ GPQQLRRLFD AARNLPNICN IPNIGACPFR AW}}<br /> '''M-3:''' {{mono|EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW}}<br /> '''M-4:''' {{mono|EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW}}<br /> ''Amino acid sequence of Mabinlins homologues are adapted from Swiss-Prot biological database of protein.''<ref name="P80351">{{UniProt Full|P80351|Sweet protein mabinlin-1}}</ref><ref name="P30233">{{UniProt Full|P30233|Sweet protein mabinlin-2}}</ref><ref name="P80352">{{UniProt Full|P80352|Sweet protein mabinlin-3}}</ref><ref name="P80353">{{UniProt Full|P80353|Sweet protein mabinlin-4}}</ref> </blockquote>
The molecular weights of Mabinlin-1, Mabinlin-3 and Mabinlin-4 are 12.3 kDa, 12.3 kDa and 11.9 kDa, respectively.<ref name="nirasawa-1994"/>
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 produced by post-translational cleavage. 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.<ref name="liu-1993"/><ref name="kohmura-1998">{{cite journal | vauthors = Kohmura M, Ariyoshi Y | title = Chemical synthesis and characterization of the sweet protein mabinlin II | journal = Biopolymers | volume = 46 | issue = 4 | pages = 215–23 | date = October 1998 | pmid = 9715665 | doi = 10.1002/(SICI)1097-0282(19981005)46:4<215::AID-BIP3>3.0.CO;2-S }}</ref>
Mabinlin-2 is the sweet-tasting protein with the highest known thermostability,<ref name="guan-2000">{{cite journal | vauthors = Guan RJ, Zheng JM, Hu Z, Wang DC | title = Crystallization and preliminary X-ray analysis of the thermostable sweet protein mabinlin II | journal = Acta Crystallographica Section D | volume = 56 | issue = Pt 7 | pages = 918–9 | date = July 2000 | pmid = 10930844 | doi = 10.1107/S0907444900005850 }}</ref> which is due to the presence of the four disulfide bridges.<ref name="nirasawa-1993">{{cite journal | vauthors = Nirasawa S, Liu X, Nishino T, Kurihara Y | title = Disulfide bridge structure of the heat-stable sweet protein mabinlin II | journal = Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology | volume = 1202 | issue = 2 | pages = 277–80 | date = October 1993 | pmid = 8399391 | doi = 10.1016/0167-4838(93)90016-K }}</ref> 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.<ref name="nirasawa-1994"/>
The B54-B64 segment of the beta chain in Mabinlin II is the primary functional domain that enables its function as a sweet protein.The segment contains the [NL/I] tetralit motif, a unique structural arrangement that contains four Asn-Leu/lle dipole units. The motif is stabilized by Pro56, Pro62, and a cysteine that is involved in a disulfide bridge, which includes CysB59-CysB11. The stabilization ensures a rigid and defined conformation.The region is one of the primary binding sites for receptor interaction such as the sweet receptor nTR2/T1R3.<ref>{{cite journal | doi=10.1016/j.jsb.2007.12.007 | title=Crystal structure of Mabinlin II: A novel structural type of sweet proteins and the main structural basis for its sweetness | date=2008 | last1=Li | first1=De-Feng | last2=Jiang | first2=Peihua | last3=Zhu | first3=De-Yu | last4=Hu | first4=Yonglin | last5=Max | first5=Marianna | last6=Wang | first6=Da-Cheng | journal=Journal of Structural Biology | volume=162 | issue=1 | pages=50–62 | pmid=18308584 }}</ref>
The sequences of Mabilins cluster with Napins ({{InterPro|IPR000617}}).
== Sweetness properties == Mabinlins sweetness were estimated to be about 100–400 times that of sucrose on molar basis, 10 times sucrose on a weight basis,<ref name="liu-1993"/><ref name="nirasawa-1994"/> which make them less sweet than thaumatin (3000 times) but elicit a similar sweetness profile.<ref name="crfsn-32-231">{{cite journal | vauthors = Kurihara Y | title = Characteristics of antisweet substances, sweet proteins, and sweetness-inducing proteins | journal = Critical Reviews in Food Science and Nutrition | volume = 32 | issue = 3 | pages = 231–52 | year = 1992 | pmid = 1418601 | doi = 10.1080/10408399209527598 }}</ref>
The sweetness of mabinlin-2 is unchanged after 48 hours incubation at 80 °C.<ref name="liu-1993"/>
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.<ref name="nirasawa-1994"/><ref name="Kurihara-1997">{{cite journal |vauthors=Kurihara Y, Nirasawa S |title=Structures and activities of sweetness-inducing substances (miraculin, curculin, strogin) and the heat-stable sweet protein, mabinlin |journal=Foods and Food Ingredients Journal of Japan |issue=174 |pages=67–74 |year=1997 |url=http://www.ffcr.or.jp/zaidan/FFCRHOME.nsf/7bd44c20b0dc562649256502001b65e9/ea044c8f392c31d5492568a20029dd20/$FILE/174-10.pdf |access-date=2007-10-01 |archive-url=https://web.archive.org/web/20130912205449/http://www.ffcr.or.jp/zaidan/FFCRHOME.nsf/7bd44c20b0dc562649256502001b65e9/ea044c8f392c31d5492568a20029dd20/$FILE/174-10.pdf |archive-date=2013-09-12 |url-status=dead }}</ref>
== 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.<ref name="kohmura-1998"/>
Mabinlin-2 has been expressed in transgenic potato tubers, but no explicit results have been reported yet.<ref name="xiong-1996">{{cite journal | vauthors = Xiong LW, Sun S | title = Molecular cloning and transgenic expression of the sweet protein mabinlin in potato tubers. | journal = Plant Physiology | date = 1996 | volume = 111 | issue = 2 | pages = 147 }}</ref> However, patents to protect production of recombinant mabinlin by cloning and DNA sequencing have been issued.<ref name="sun-2000">{{cite patent | country = US | number = 6051758 | status = patent| inventor1-first=Samuel S.M.|inventor1-last=Sun| inventor2-first=Liwen|inventor2-last=Xiong| inventor3-first=Zhong|inventor3-last=Hu| inventor4-first=Hang|inventor4-last=Chen| assign = University of Hawaii | title = Recombinant Sweet protein Mabinlin | gdate = 2000-04-18 }}</ref>
== See also == *Brazzein *Monellin *Pentadin *Thaumatin
== References == {{Reflist}}
== External links == *{{Commons category-inline}}
Category:Sugar substitutes Category:Proteins