ANTIFUNGAL PROTEINSBY SREE REMYA.S

II MSC BIOTECHNOLOGY

CONTENTS• INTRODUCTION

• FUNGAL CELL WALL

• ANTIFUNGAL PROTEINS

• CLASSES OF ANTIFUNGAL PROTEINS & THEIR MECHANISMS

• CONCLUSION

INRODUCTIONFungi are amazing organisms, which can

grow in any surfaceFungi are proficient at colonizing & using

plants, humans & animals as substrateThe fungal cell wall protects the organisms

& relays signals for invasion& infection of a plant, animal or a human host

Fungi are extremely diverse group of organisms &some plants have antifungal activity

FUNGAL CELL WALL

ANTIFUNGAL PROTEINSPlants are exposed to large number of

pathogenic fungiAlthough plants do not have an immune

system, but they have a defense mechanism including antifungal activity

There are hundred’s of antifungal peptides & proteins known, with more being discovered almost daily

CLASSES OF ANTIFUNGAL PROTEINSo 13 CLASSES OF ANTIFUNGAL PROTEINS

ARE PRESENT: PR PROTEINSPR-1 PROTEINSPR-2 PROTEINS (beta glucanases)PR-3 PROTEINS(chitinases)PR-4 PROTEINS(chitin binding ) proteinsPR-5 PROTEINS(TL)DEFENSINSCYCLOPHILIN- LIKE PROTEINS

CONT….RIPsKILLER PROTEINS (KILLER TOXINS)PROTEASE INHIBITORSOTHER PROTEINS

ANTIFUNGAL PROTEIN

PR PROTEINSPlants exposed to pathogens such as

fungi& viruses produce low molecular weight antimicrobial compounds called phytoalexins

These plant proteins called pathogenesis related (PR) proteins , are divided into 5 groups, PR-1,-2,-3,-4,-5, based on serological& amino acid sequence analysis

The 5 classical groups of PR proteins has 2 subclasses:

Cont….A basic subclass found in plant cell vacuoleAn acidic subclass found in the

extracellular space

PR-1 proteins PR-1 proteins accumulates to high levels

after pathogen infection& are antifungal both in plants& in vitro

PR-1proteins have been found in wheat, rice , maize, tobacco

PR-1proteins cont….PR-1 proteins have antifungal activity at

the micro molar level against no: of plant pathogenic fungi including Uromyces fabae, Phytophthora infestans,Erysiphe graminis

PR-1proteins mechanismis unknownPR-2 PROTEINSPR-2 have(1,3)beta glucanase activity in

vitro & are grouped into 3 classes on the basis of aminoacid sequence analysis

PR-2 PROTEINSThis proteins found in plants like tobacco,

peas, grains & fruitsThe proteins are active at wide range of

fungi including human& plant pathogen(Rhizoctonia solani, C. albicans, A. fumigatus)

The antifungal activity of PR-2proteins are demonstrated by no: of invitro enzymes

BETA GLUCANASES

PR-3 PROTEINS(chitinase)A no: of enzymatic assays describes PR-

3proteins to have in vitro chitinase activityChitinases are isolated from fungi, plants

(tobacco, cucumber, beans)& bacteria have potent antifungal activity against human& plant pathogens including T. reesi, Alternia solani, A.radicina,F.oxysporum)

PR-4(chitin binding ) proteinsPR-4proteins have

molecular mass of 13- 14.5 KDa

PR-4proteins are isolated from potato, tobacco, barley , pumpkins& many other plant

PR-4 PROTEINS CONT….Chitin binding proteins& have antifungal

activity but are not PR proteins have been isolated from bacteria, plants, insects

Fungi inhibited by these proteins include plant& human pathogens eg: Paecilomyces variotii, F.oxysporum, Aspergillus.sp,A. brassicola

PR-5 ( TL) PROTEINSPR-5 proteins share significant homology

to thaumatin & are known as TLproteins

Cont…TL proteins have been isolated from A.

thaliana, pumpkin, wheat ,riceThe highly stabilized structure of PR-5 are

resistant to protease degradationMechanism is not knownThese proteins they are fungicidal against

a wide no: of plant& human pathogens, zeamatin protein has shown efficacy in murine vaginal model of C. albicans

DEFENSINSDefensins are low molecular mass

cysteine rich proteins found in mammals, fungi ,insects & plants

The insecect & mammalian defensins are quiet small & form voltage depedent ion channels in plasma membrane

The treatement of hyphae with the defensins from radish & dhalia cause k+ efflux & Ca+ uptake through binding to specific cell membrane receptors

COND…. Defensins have the ability to inhibit human&

fungal pathogens including B.cinerea, F.oxysporoum,F.solani & C.albicans at micromolar levels

CYCLOPHILIN LIKE PROTEIN Cyclophilins are conserved group of proteins –

that are intracellular receptors for cyclosporin & is found in bacteria, plant, animal,fungi

A protein isolated from mung bean is called mungin. Antifungal mechanism is not known

RIPsRIPs are RNA N- glucosidase that

depurinates Rrna,result inarrest of protein synthesis due to ribosome damage

Plant RIPs inhibit mammalian,bacterial, plant, fungal protein synthesis

RIPs have been isolated from Pisum sativum, Viscum album, & from fungi – A.giganteus

RIPs have intrinsic antifungal activity – have ability to inactivate fungal ribosomes invitro.

KILLER PROTEINS (KILLER TOXINS)A no: of yeast secrete proteins that are

lethal to sensitive fungal cells.These proteins are killer toxins are encoded by either by double stranded DNA,linear double stranded plasmid DNA

CONT… Fungal cells secrete a killer toxin are

resistant to their own toxin but are sensitive to other toxin

Kulveromyces lactis& several Pichia species secrete a no: of killer toxin

Killer proteins can disrupt cell wall synthesis ,DNA synthesis,& k+ channel activity – any of these effect leads to inhibition of fungal cell growth

PROTEIN INHIBITORSProtein inhibitors of serine & cysteine

protease have emerged as antifungal proteins that have potent activity against plant & animal pathogens.

GRAPH SHOWING THE POTENT ACTIVITY

CONT….Cysteine protease inhibitors are isolated

from a no: of plants & from a group of cystatins, the phytocystatins

Phytocystatins are active against plant pathogens such as F. solani,T.reesi

CURRENT INVENTIONSAntifungal activity work is carried out

world wideViridin a novel protein isolated from

culture protein T. viridae –molecular mass 65 kDa is active against fungi at 6 micrometer

Snakin -1 is such a novel protein isolated from potato

CONCLUSIONAntifungal proteins & polypeptides have

been isolated from diverse group of organisms

The range of fungi inhibited by antifungal proteins are extremely broad, & studies about antifungal proteins are carried out widely