Mediterranean Biochemical Network

Structural and functional studies of respiratory proteins

Scientists from the Italian Universities of Cagliari, Sassari and Roma, the Egyptian University of Mansoura and the University of Malta, together with the Ministry of Interior (Game Funds) of Nicosia (Cyprus) are involved in the project indicated above in the title.
Their research work lies in structural and functional studies of respiratory proteins such as hemoglobins, with the aim of discovering various complex regulatory mechanisms operative at molecular level and designed to fulfil the physiological requirement of a given species.
These mechanisms are based on the thermodinamic connection between the binding of heterotropic effectors (protons, CO2, chloride ions and organic phosphates) and the reaction with O2.

Another important feature of the reaction of hemoglobins with O2 is its temperature-dependence, which is governed by the associated overall enthalpy change. In the past a lot of hemoglobins from mammals, birds, fish and other vertebrates have been investigated by our group through comparative studies at biochemical, physiological and molecular levels; the data obtained by this experimental approach may provide useful information on the features involved in the evolutionary processes of hemoglobin in vertebrates.
The study of Hb from red deer, for instance, whose habitat varies widely with respect to temperature and altitude, may give further information on molecular adaptive mechanisms to habitat, if compared to other ruminant Hbs.

The significance of the studies on abnormal human hemoglobin (Hb) is widely known. As "natural derivatives", mutant Hbs provide the best example of the manner in which the structure influences the function of a protein and expand knowledge on the role played by each amino acid in the function of the protein.
Mutant Hbs, moreover, are useful in understanding the mechanisms of globin gene expression, RNA processing, protein synthesis and stability, as well as in understanding the nature, type and effect of mutations, and so on. Qualitative hemoglobinopathies are due to a wide range of genetic defects such as the production of structurally unstable globins or Hb with altered O2 binding ability, both characterized by intra-erythrocytic damages of different extent. Intra-erythrocytic changes most probably due to alterations of the dissociation curve of a wide spectrum of variant Hb still remain to be described. Similarly, data on the effects of an abnormal synthesis of (normal) fetal Hb, or on the possible effects of the presence of a mutant fetal Hb, on the fetus as well as data on clinical and biochemical relevance of maternal Hb with high O2 affinity on fetal pain, is insufficient.

At present, publications due to our group are the only dealing with this biochemical aspect. For the above reasons the interest in this field is continuing so that some 20 new variants are described each year all over the world. In the Italian population, the number of documented variants is 57 and in the island of Sardinia some of them reach considerable frequencies.
The remarkable range of morphology and adaptation among animals is testified by the diversity of structure and function of their O2-carrying proteins. Though human Hbs received and extraordinarily higher attention and interest, it is unequivocally recognized that a full understanding of the molecular genetics, biochemistry, and physiology of Hbs depends on comparative studies. Investigation and comparison of a wide span of animal Hbs provides an impressive glimpse of molecular evolution, is of importance in understanding associations between functional behavior and environmental adaptation, is at the basis for the knowledge of the multiplicity of effects associated to the presence of a particular amino acid in a particular sub-unit position.
This is exceedingly important due to the high structural and functional intra-species polymorphism displayed by several vertebrates. Amongst the number of possible examples, the discovery of the Root effect and of its role in some fish Hb and the observation that ovi-caprines, due to a re-activable globin gene, are able to "switch" from the adult to a pre-adult Hb during physiological or experimental anemia and hypoxia, represent paradigms. The latter is an unexpected biochemical and molecular model useful in studies on the control of gene expression. Thanks to the experience gained in the past years (see a list of recent, selected, publications), which allowed us to discover and study several human Hb variants and abnormal Hbs in the human population (adult and newborn) of Sardinia and of other Mediterranean countries in order to extend the knowledge on epidemiological and biochemical aspects of such a genetic defects.

The research activity has the thalassemic genes, and to describe and interpret the Hb polymorphism in some vertebrates, the research activity of our group has the object to extend the search for additional aim of the detection of the molecular basis responsible for the mutation by means of the sequencing of the affected globin gene. Methods for the identification at the screening level will be also described and proposed to researchers of developing countries.
The study will also examine the Hb polymorphism, the structure of tetramers and of constituent globins, the nucleotide sequence of structural genes of the most representative vertebrates that, due to their habitat, spreading, and phylogenetic aspects may represent useful models of evolution and adaptation.

Considering that animals living in geographically restricted areas may be genetically stable, our study deals with:
a) the detection of Hb polymorphism of vertebrates living in Sardinia, Corsica, Cyprus, Chios, Turkey, Giordania, Iran, Egypt, etc.
b) the determination of Hb structure, its ability in increasing the polymorphism and improving adaptation to different environmental conditions;
c) detection of globin gene sequence;
d) comparison of sequences differing in as little as one position.

The tasks of our Unit are consistent with the application of newer methodologies for the separation and identification of Hb and of its polymorphism, for subsequent structural studies, identification of DNA polymorphism, sequencing of the normal and abnormal globin gene. Result will be essential in interpreting molecular mechanisms involved in adaptation to environment.

Universities involved in this project:

University of Cagliari - Italy

Prof. Angelo Cau
Prof. Marcella Corda
Prof. Anna Maria Deiana
Prof. Irene Messana
Prof. Mariagiuseppina Pellegrini
Dr. Maria Teresa Sanna
Dr. Alessandra Olianas
Dr. Antonella Fais

University of Sassari - Italy

Prof. Bruno Masala
Prof. Laura Manca

Universities of Roma - Italy

Prof. Paolo Ascenzi (Roma III)
Prof. Massimo Coletta (Tor Vergata)
Prof. Bruno Giardina (Catholic University)
Prof. Massimo Castagnola (Catholic University)
Prof. Cecilia Zuppi (Catholic University)

University of Corte - France

Dr. Paolo Franceschi

University of Mansoura - Egypt

Prof. Said el Sherbini

Ministry of Interior (Game Funds) of Nicosia (Cyprus)

Dr. Elefterios Hadjisterkotis