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Following several years of illness Franc Guben{ek died on
August 17th 2010. 
Franc Guben{ek was born in 1937. In 1961 he graduated in
physical chemistry at the Technical faculty, University of
Ljubljana and was immediately appointed to the Department of
Radiobiology in the then Nuclear Institute, today the Jo`ef
Stefan Institute (JSI) in Ljubljana. He received his Ph.D. in 1965
in the field of physical chemistry at the Faculty of Natural
Sciences and Technology, University of Ljubljana. Soon after
the defence of his doctoral thesis he obtained a Fulbright fellow-
ship and, in 1967, started his post-doctoral study at the
University in Arizona, Tucson with John Rupley. There he en-
countered protein science, then a very promising and rapidly de-
veloping field, which attracted him at once and to which he be-
came bound for the rest of his life. 
Following his return from the USA, he started his life work on
protein toxins in the group of Professor Drago Lebez at the JSI,
the founder of toxinology research in Slovenia. When Lebez left
the JSI in 1976, Franc Guben{ek – Fran~ek to his colleagues and
friends – took his position and assumed part of his toxicological
problematics – he focused on the protein components of the ven-
om of the most venomous European snake, the horn-nosed viper,
Vipera ammodytes ammodytes. He was especially interested in
proteins with phospholipase activity as one of the major pharma-
cologically active components of the venom, showing them to
belong to the group of secreted phospholipases A2 (sPLA2s).
Today, those that possess strong presynaptic neurotoxicity and
anticoagulant activity are known as ammodytoxins and those
that are myotoxicity or not toxic, ammodytins. At the beginning
of the 1980s Fran~ek was attracted by the structure of proteins.
Initially, he was studying their secondary structure, using circu-
lar dichroism spectroscopy. Even more important was his role in
introducing protein primary structure determination into
Slovenia and, under his lead, the first protein primary structures
were determined. Based on complementary methodological ap-
proaches, he directed his group in the early 1990s into four sep-
arate pathways of snake venom research. 
First, by developing an immunological approach they mapped
the structure of the so-called »toxic site« on the molecule of am-
modytoxin. To accomplish this task they introduced the technol-
ogy of preparing monoclonal and site-directed antibodies into
Slovenia. 
Secondly, they introduced molecular biology and protein engi-
neering into toxinological studies. They determined cDNA se-
quences of all the ammodytoxins and ammodytins. The first
method for preparing recombinant ammodytoxin in E. coli was
then successfully developed, followed by highly effective bacte-
rial production of these toxins. This formed the basis for the
biosynthesis of a number of ammodytoxin mutants over the fol-
lowing years. Designed replacements of amino acid residues re-
vealed the complexity of the »neurotoxic site« in the molecule of
ammodytoxin. In this way, the areas of interaction of the am-
modytoxin molecule with various receptors, and the role of par-
ticular amino acid residues in the molecule in binding to phos-
pholipid membranes were determined, a step important in deter-
mining the specificity and enzyme activity of every sPLA2. 
A big challenge was, and still is, to understand the mechanism of
blockade of neuromuscular communication by sPLA2 toxins at
the molecular level. So, thirdly, they started to look for the reason
for the specific action of ammodytoxins on the presynaptic mem-
brane of the motoneuron by introducing methods to study mem-
brane proteins and by characterizing membrane receptors. The
key to identification of the first binding proteins for ammodytox-
in in the presynaptic membranes of bovine cerebral cortex was
Dedicated to the memory of the
late Prof. Dr. Franc Guben{ek
Memorial Issue
ActaChimicaSlovenica
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the successful development of a method for preparing radioac-
tively labelled ammodytoxin. The discovery and description of
additional high-affinity membrane receptors for ammodytoxin in
different nervous tissues followed. It was a big surprise when the
first intracellular high-affinity binding protein for ammodytoxin
was found to be calmodulin. However, soon after, further intra-
cellular ammodytoxin-binding proteins were found – 14-3-3 pro-
teins, like calmodulin also localized in the cytosol, and R25, a
protein in the mitochondrial membrane. Doubt concerning the
dogma of exclusively extracellular action of sPLA2s was further
strengthened with the first proofs about the entrance of ammody-
toxin into nerve cells in culture and its biological activity in the
cytosol of a eukaryotic cell. Following the demonstration of the
possibility of sPLA2 action in the cytosol, mitochondria and nu-
cleus, various explanations for the numerous effects of these en-
zymes on mammalian cells have been advanced.
Fourthly, Fran~ek and his colleagues entered the exciting area of
molecular evolution. They studied the evolution of toxins, DNA
transposable elements and the structure of their genes. In this
particular activity of his group it is especially important to em-
phasize the discovery of a novel mobile element of DNA, retro-
transposon ART-2 or Bov-B LINE. They clearly demonstrated
that this retrotransposon moved, more than 45 million years ago,
from the genome of an evolutionarily old snake to the genome of
an ancestor of today’s ruminants. This first, clear experimental
demonstration of the so-called horizontal transfer of genetic ma-
terial between such distant classes of vertebrates stimulated sig-
nificant interest in the scientific community and well merited
publication in Nature Genetics.
One of Fran~ek’s great qualities was that he trusted us, his
younger colleagues, and allowed us to take initiatives. He never
tried to enforce his opinion but he polished many of our ideas in
constructive dialogue, with his extensive knowledge and ingenu-
ity. One consequence of this characteristic is the existence today
at the JSI of the only group of experts in Slovenia trained and
equipped to perform high-throughput yeast genomics experi-
ments, operating in the department that evolved from his research
group. With this facility the picture of the mechanism of action of
neurotoxic sPLA2s has been refined and, in addition, the ability to
study the mechanisms of action of drugs, and lipid-associated and
lipid-mediated diseases in humans has been facilitated. 
His group collaborated extensively with prominent research
groups from all over the world. With his collaborators he pub-
lished about 140 research papers in the best journals for the area
of investigation. With them he acquired high international recog-
nition for himself and his group in the field of toxinology. In ac-
knowledgement of his important achievements in toxinology he
was elected, from 1989 to 1996, President of the European
Section of the International Society on Toxinology (EIST) and,
from 1997 to 2000, President of the worldwide IST.
He organized several international scientific conferences and took
part in many scientific boards of meetings in Slovenia and abroad.
Three times, in 1977, 1989 and 2004, he and his team organized
the EIST symposia. For many years he served as a member of the
Editorial Boards of Toxicon and Acta Chimica Slovenica. 
His work as a teacher, starting in 1974, was also very rich. In
1986 he became a Full Professor of biochemistry at the
University of Ljubljana. He taught various areas of the subject at
undergraduate and postgraduate levels in the Faculty of Che-
mistry and Chemical Technology (FCCT), Biotechnical Faculty
and Medical Faculty. In 1997 he was fully engaged at the FCCT,
in the Chair of Biochemistry which he then led until his retire-
ment in 2004. His leading role in the creation and organization
of the new, independent study of biochemistry at the FCCT has
to be especially emphasized. Fran~ek was an experienced men-
tor and a great motivator of researchers. Under his leadership
many students graduated and presented their master’s and doc-
toral theses. Many of them hold important positions today in
Slovenian and international institutions and in industry. 
Scientific, pedagogical and group-leading activities did not pre-
vent Fran~ek from dedicating his energy to organization and pro-
motion of the development of biochemistry and molecular biolo-
gy in the broader community. In this respect, he was a very active
member of the Slovenian Biochemical Society from its begin-
ning. From 1989 to 1998, he also headed the Society. From 1997
he was a representative of the Republic of Slovenia in the
European Molecular Biology Conference (EMBC). The numer-
ous important duties that he accepted, he always accomplished
accurately and comprehensively. Besides his professional work
he carried out a number of responsible organisational and execu-
tive functions at the JSI, the most important being a member of its
Executive Board from 1992 and its President from 1997 to 2005.
His scientific achievements and status were recognized interna-
tionally by his membership of the European Molecular Biology
Organization (EMBO) to which he was elected in 1998 as the
first Slovenian scientist. In 1992 he was nominated as an
Honorary Visiting Professor at the Guangxi Medical University
in Nanning, China. In 1996 he was honoured by the Croatian
Biochemical Society. Fran~ek also received several domestic
awards, including the Zois Award in 1997. For his substantial
contribution to the development and organization of biochem-
istry and molecular biology in Slovenia he was nominated in
2008 as an Honorary Member of the Slovenian Biochemical
Society. In 2003, he was elected a member the Slovenian Aca-
demy of Sciences and Arts. 
Sadly, progressive Alzheimer’s disease prevented Fran~ek from
continuing his work and collaboration with the research team
that he created and headed until his retirement in 2004. His ex-
tensive legacy, however, facilitated the evolution of his research
group into a strong and independent department, the Department
of Molecular and Biomedical Sciences at the JSI.
We, his colleagues and friends, are grateful to him for all he gave
us, as scientist and friend. For this reason, we will always keep
him in cherished memory. We all remember Frank’s boisterous
laughter, the twinkle in his eyes during meetings among friends,
and his sharp and witty jokes. These memories will linger on and
act as an inspiration to younger scientists.
In this special issue of Acta Chimica Slovenica, dedicated to his
memory, you will find fourteen articles written by some of the
World’s prominent toxinologists to whom he was very close. 
Igor Kri`aj, Guest Editor
Department of Molecular and Biomedical Sciences, 
Jo`ef Stefan Institute, Ljubljana, Slovenia
Ponnampalam Gopalakrishnakone, President of the IST
Venom and Toxin Research Programme, Yong Loo Lin School 
of Medicine, National University of Singapore, Singapore.
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