BanLec (also BanLec-I or Banana lectin) is a

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar Moiety (chemistry), groups that are part of other molecules, so cause agglutination (biology), agglutination of particular cells or precipitation of glycoconjugates an ...

from the

jacalin Jacalin is a plant-based lectin, but not a legume lectin, found in jackfruit. It has been studied for capturing O-glycoproteins such as mucins and IgA1, for potential applications in human immunology. Jacalin belongs to a family of galactose-bind ...

-related lectin family isolated from the fruit of the

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...

s ''

Musa acuminata ''Musa acuminata'' is a species of banana native to South Asia, Southern Asia, its range comprising the Indian subcontinent and Southeast Asia. Many of the modern edible dessert bananas are derived from this species, although some are hybrids wi ...

'' and ''

Musa balbisiana ''Musa balbisiana'', also known simply as plantain, is a wild-type species of banana. It is one of the ancestors of modern cultivated bananas, along with '' Musa acuminata''. Description It grows lush leaves in clumps with a more upright habit ...

''. BanLec is one of the predominant

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s in the pulp of ripe bananas and has binding specificity for

mannose Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylatio ...

and mannose-containing

oligosaccharide An oligosaccharide (; ) is a carbohydrate, saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including Cell–cell recognition, cell recognition and ce ...

s. A 2010 study reported that BanLec was a potent inhibitor of

HIV The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the im ...

replication.

Activity

BanLec has a number of similarities to

Concanavalin A Concanavalin A (ConA) is a lectin (carbohydrate-binding protein) originally extracted from the jack-bean (''Canavalia ensiformis''). It is a member of the legume lectin family. It binds specifically to certain structures found in various sugars, ...

and binds to

-related

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

structures. It was discovered due to its highly

immunogenic Immunogenicity is the ability of a foreign substance, such as an antigen, to provoke an immune response in the body of a human or other animal. It may be wanted or unwanted: * Wanted immunogenicity typically relates to vaccines, where the injectio ...

properties—BanLec induces a strong IgG4

antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

response—and appears to be an important

antigen In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

involved in banana allergies. BanLec expression can be induced by the

plant hormone Plant hormones (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis, the regulation of Organ (anat ...

methyl jasmonate.

Structure and stability

BanLec exists as a

homodimer In biochemistry, a protein dimer is a macromolecular complex or protein multimer, multimer formed by two protein monomers, or single proteins, which are usually Non-covalent interaction, non-covalently bound. Many macromolecules, such as proteins ...

of two identical 15 kDa subunits and has also been reported as a tetramer complex. The protein is highly stable, unfolding only at high temperatures All jacalin-related lectins feature type I beta-prism folding motifs (the beta-prism I fold is like a perfect beta-prism with each side made up of a four-stranded greek key motif), but BanLec is the first jacalin-related lectin from the

monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are flowering plants whose seeds contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but ...

family of plants, while all other members are

dicot The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, ...

s; other monocot mannose-binding lectins exhibit beta-prism II folding instead. BanLec features strong intersubunit interactions with high levels of

hydrogen bond In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

ing and water bridges allowing resistance to denaturing when exposed to high temperatures or high concentrations of chaotropes such as guanidium hydrochloride.

Crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

s of BanLec suggest that the lectin has two

saccharide A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' m ...

binding sites.

HIV inhibition

In 2010, BanLec was reported to be a potent inhibitor of

replication."Study: Chemical in Bananas Could Help Fight HIV"

Fox News Channel The Fox News Channel (FNC), commonly known as Fox News, is an American multinational conservative news and political commentary television channel and website based in New York City, U.S. It is owned by Fox News Media, which itself is ow ...

, March 16, 2010 Researchers at the

University of Michigan The University of Michigan (U-M, U of M, or Michigan) is a public university, public research university in Ann Arbor, Michigan, United States. Founded in 1817, it is the oldest institution of higher education in the state. The University of Mi ...

determined that BanLec bound to the

HIV-1 The subtypes of HIV include two main subtypes, known as HIV type 1 (HIV-1) and HIV type 2 (HIV-2). These subtypes have distinct genetic differences and are associated with different epidemiological patterns and clinical characteristics. HIV-1 e ...

envelope protein gp120, which is high in sugar content, inhibiting viral entry into human cells. The researchers suggest that such an inhibitor of HIV infection may find use as a

topical A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...

treatment, such as a

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

microbicide An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...

, and may be cheaper to produce than current antiviral topical treatments."Protein in bananas could help block spread of HIV, University of Michigan researchers say"
AnnArbor.com, March 15, 2010

References

{{Lectins Lectins Plant lectins