Max Planck Institute in Martinsried near Munich turned out to be crucial for the future research in Ljubljana. Vito’s contacts with Robert, and particularly with Wolfram Bode, were essential for the major progress in the under- standing of molecular mechanisms of cathepsin-cystatin interactions. The crystal structure of chicken cystatin and the famous elephant trunk model (Bode et al., 1988) were confirmed by the crystal structure of the stefin B/papain complex (Stubbs et al., 1990). A further outcome of this relationship was the crystal structure of the first cathep- sin (cathepsin B), determined by Musil et al. (1991). This work was also done in collaboration with another of Vito’s old friends and colleagues, Nobuhiko Katunuma from Japan. Finally Vito managed to establish a crystallogra- phy group in his Department in Ljubljana, headed by Dušan Turk, who was trained in this field in Robert Hu- ber’s laboratory in early 1990s. Although initially spread between Ljubljana and Munich (crystallization and com- Biol. Chem., Vol. 384, pp. 833 – 836, June 2003 · Copyright © by Walter de Gruyter · Berlin · New York Vito Turk, born in Osijek (now the Republic of Croatia) in 1937, devoted almost his entire scientific life to research on lysosomal proteases. Starting at the Department of Radiology in the early 1960s he initially worked on aspar- tic proteases, primarily cathepsin D. Affinity chromatog- raphy was developed as a special technique for protein purification (Smith and Turk, 1974), and later on used widely for the purification of cysteine proteases and their inhibitors. The (renamed) Department of Biochemistry (now Department of Biochemistry and Molecular Biology) was led by Vito with great enthusiasm for 25 years, since 1971. In the 1970s research moved more and more to- ward cysteine proteases, and as the first new acidic sulfhydryl protease cathepsin S was found (Turnšek et al., 1975, 1977). The 1980s were the golden years for the work on hu- man papain-like cathepsins and their inhibitors. Cys- tatins emerged as endogenous inhibitors of cathepsins with important contributions from Vito’s group, which dis- covered and sequenced several of them, including stefin A, named after the Jozef Stefan Institute (JSI). The first two sequences elucidated in collaboration with the team headed by Hans Fritz in Munich, Germany, were pub- lished in this journal, at that time entitled Hoppe-Seyler’s Zeitschrift für Physiologische Chemie (Turk et al., 1983; Machleidt et al., 1983). Another exciting discovery in the inhibitor field was the finding that larger plasma proteins, the kininogens, also inhibit cysteine proteases (Müller- Esterl et al., 1985). A decade later the story continued and kininogens were shown to simultaneously bind two molecules of cysteine proteases, thus clarifying a long- lasting enigma (Turk et al., 1995a). Antiviral activity of the cystatins, determined in collaboration with Bruce Korant, was another important contribution from Vito’s group (Korant et al., 1986). Amino acid sequencing was, with the help of the Mu- nich colleagues (especially Werner Machleidt), estab- lished in the lab in Ljubljana and resulted in determination of amino acid sequences of human cathepsins B, H and L (Ritonja et al., 1985, 1988). This collaboration and friendship extended for many years and Vito and Hans remained in close contact even after the major research areas of the two groups separated and they organized numerous scientific meetings together, including the Winter Schools on recent developments in the field, pri- marily for junior scientists (the first one in Slovenia in 1981) and the Brdo Conferences on Protease Inhibitors. Close collaboration with Robert Huber’s group at the Editorial Vito Turk – 30 Years of Research on Cysteine Proteases and Their Inhibitors Professor Vito Turk Brought to you by | University of Michigan Authenticated Download Date | 5/20/15 6:50 AM