Dinakar M Salunke
Articles written in Journal of Biosciences
Volume 6 Issue 4 October 1984 pp 357-377
Although globular proteins are endowed with well defined three-dimensional structures, they exhibit substantial mobility within the framework of the given three-dimensional structure. The different types of mobility found in proteins by and large correspond to the different levels of organisational hierarchy in protein architecture. They are of considerable structural and functional significance, and can be broadly classified into (a) thermal and conformational fluctuations, (b) segmental mobility, (c) interdomain mobility and (d) intersubunit mobility. Protein crystallographic studies has provided a wealth of information on all of them. The temperature factors derived from X-ray diffraction studies provide a measure of atomic displacements caused by thermal and conformational fluctuations. The variation of displacement along the polypeptide chain have provided functionally significant information on the flexibility of different regions of the molecule in proteins such as myoglobin, lysozyme and prealbumin. Segmental mobility often involves the movement of a region or a segment of a molecule with respect to the rest, as in the transition between the apo and the holo structures of lactate dehydrogenase. It may also involve rigidification of a disordered region of the molecule as in the activation of the zymogens of serine proteases. Transitions between the apo and the holo structures of alcohol dehydrogenase, and between the free and the sugar bound forms of hexokinase, are good examples of interdomain mobility caused by hinge-bending. The capability of different domains to move semi-independently contributes greatly to the versatility of immunoglobulin molecules. Interdomain mobility in citrate synthase appears to be more complex and its study has led to an alternative description of domain closure. The classical and the most thoroughly studied case of intersubunit mobility is that in haemoglobin. The stereochemical mechanism of the action of this allosteric protein clearly brings out the functional subtilities that could be achieved through intersubunit movements. In addition to ligand binding and activation, environmental changes also often cause structural transformations. The reversible transformation between 2 Zn insulin and 4 Zn insulin is caused by changes in the ionic strength of the medium. Adenylate Kinase provides a good example for functionally significant reversible conformational transitions induced by variation in pH. Available evidences indicate that reversible structural transformations in proteins could also be caused by changes in the aqueous environment, including those in the amount of water surrounding protein molecules.
Volume 24 Issue S1 March 1999 pp 5-31
F Parak A Ostermann G U Nienhaus Nobuo Niimura William A Eaton Stephen J Hagen Eric R Henry James Hofrichter Gouri Jas Lisa Lapidus Victor Muñoz Chih-chen Wang Abani Bhuyan Javant Udgaonkar Heinz Rüterians Derek N Woolfson M D Finucane J H Lees M J Pandya G Spooner M Tuna Wilma K Olson K V R Chary E Westhof I G Wool C C Correll V I Ivanov S A Bondarenko E M Zdobnov A D Beniaminov E E Minyat N B Ulyanov Dale B Wigley Nobuo Shimamoto Takashi Kinebuchi Hiroyuki Kabata Osamu Kurosawa Masao Washizu Barbara Baird David Holowka H Belrhali P Nollert A Royant J P Rosenbusch E M Landau E Pebav-Peyroula Anil K Lala Patrick R D’Silva Daniela Pietrobon Paolo Pinton Paulo Magalhaes Anna Chiesa Marisa Brini Tullio Pozzan Rosario Rizzuto M Montai Shu-Rong Wang José L Carrascosa B Bhattacharyya Ian A Wilson Dinakar M Salunke Kurt Drickamer Anne Imberty A Surolia Louise N Johnson Michal Neeman S M Prince K McLuskey R J Cogdell K McAuley N W Isaacs G Venturoli F Drepper J C Williams J P Allen X Lin P Mathis R van Grondelle Wolfgang Junge T Tsukihara K Shinzawa-Itoh R Nakashima E Yamashita M J Fei N Inoue T Tomizaki C Peters Libeu S Yoshikawa Patrick Chaussepied Keiichi Namba Marie-France Carlier Fariza Ressacl Valerie Laurent Thomas Loisel Coumaran Egile Philippe Sansonetti Dominique Pantaloni Manju Bansal E W Knapp M G Ullmann A Amadei B L de Groot M A Ceruso M Paci H J C Berendsen A Di Nola V Di Francesco P J Munson J Garnier Sung-Hou Kim Jean-Michel Claverie Ian C P Smith P T Callaghan Bruce Cornell Ratna S Phadke Kazuhiko Kinosita D Goldfarb I Qromov C Shutter I Pecht P Manikandan R Carmieli T Shane David S Moss Clare E Sansom Jeremy K Cockcroft Ian J Tickle Huub C P Driessen J Raul Grigera Ramen K Poddar Charles R Cantor Barry Robson Jean Garnier John Helliwell Sunney I Chan Ronald Rock
Volume 26 Issue 3 September 2001 pp 325-332
We have earlier reported that overexpression of the gene encoding human hyaluronan-binding protein (HABP1) is functionally active, as it binds specifically with hyaluronan (HA). In this communication, we confirm the collapse of the filamentous and branched structure of HA by interaction with increasing concentrations of recombinant-HABP1 (rHABP1). HA is the reported ligand of rHABP1. Here, we show the affinity of rHABP1 towards D-mannosylated albumin (DMA) by overlay assay and purification using a DMA affinity column. Our data suggests that DMA is another ligand for HABP1. Furthermore, we have observed that DMA inhibits the binding of HA in a concentration-dependent manner, suggesting its multiligand affinity amongst carbohydrates. rHABP1 shows differential affinity towards HA and DMA which depends on pH and ionic strength. These data suggest that affinity of rHABP1 towards different ligands is regulated by the microenvironment.
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