AG Filamentous fungi



Mode of action of the Antifungal Protein from Aspergillus giganteus

Introduction

Fig. 1: The Antifungal Protein from Aspegillus giganteus (Lacadena et al. 1995)
The imperfect ascomycete Aspergillus giganteus secretes two small basic proteins with an antimicrobial activity, namely the alpha-Sarcin and the Antifungal Protein (AFP). Both proteins were first isolated by Olson et al. (1965). The antimicrobial activity of alpha-Sarcin is due to its ribonuclease activity, whereas for AFP no mode of action is known. From previous work it is known that AFP consists out of 51 amino acid residues and has a molecular weight of 5.8kDa. The structure of the protein is stabilized by four disulfide bridges. Campos-Olivas et al. (1995) could show that the folding of the protein consists of five antiparallel b-strands, defining a compact b-barrel. AFP inhibits the growth of several filamentous ascomycetes. The protein has no effect on the growth of yeast and bacteria.



Fig. 2: Features of the Antifungal Protein from Aspergillus giganteus
Mode of action of the Antifungal Protein.

The Antifungal Protein (AFP) from Aspergillus giganteus belongs to a group of antimicrobial peptides which are all small basic proteins with high cysteine content.
Fig. 3: Proposed mode of action for antimicrobial peptides (Tossi et al. 2000)
(Click to enlarge)
The most prominent members of this group are the defensines which are found in plants, insects, and mammals and most often have a broad antimicrobial effect. Some plant defensines interact with phospholipids which subsequently leads to a permeabilization of the cytoplasma-membrane (Thevissen et al.). Although AFP shares some structural features with these proteins, it only inhibits the growth of several filamentous fungi, mainly from the genera Fusarium and Aspergillus.



Aim of the project

Fig. 4: Localization of FITC labelled Antifungal Protein in different fungi
The aim of this project is to find out more about the mode of action of the Antifungal Protein. The main questions to be addressed are:
To find answers to these questions the following methods are used:
Contact:
Torsten Theis
Tel: +49 30 314 72271
E-Mail: T.Theis@LB.tu-berlin.de



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Last Update: 02 / 2002