Jan Kraus, Ph.D., Basel University, 1972
Professor Pediatrics
Molecular Basis of Inherited Human Disease
 |
|
|
|
|
My laboratory studies the molecular basis of two inherited metabolic disorders associated with deficiency of cystathionine ß-synthase (CBS) and propionyl CoA carboxylase (PCC). CBS is a crucial regulator of serum levels of the thrombogenic amino acid homocysteine (Hcy) and is crucial for the tissue specific biosynthesis of cysteine. CBS deficiency is the most common cause of homocystinuria, an inherited autosomal recessive metabolic disease that if untreated, causes skeletal abnormalities, dislocated optic lenses, mental retardation and a dramatically increased incidence of thromboembolic disease. Mildly elevated plasma Hcy in humans has also been identified as an independent risk factor for cardiovascular and thromboembolic disease. Increasing numbers of epidemiological studies are also finding an association between elevated Hcy and neurodegenerative disorders such as Alzheimer's and Parkinson's disease. The crucial role of CBS in the regulation of plasma Hcy has lead to increasing interest in the mechanisms that regulate this enzyme and the cellular consequences of its dysfunction. Currently, we are applying a range of approaches including functional genomics, transgenic mouse models, X-ray crystallography, molecular cell biology and protein biochemistry to investigate the etiology of the various disease states associated with elevated Hcy due to impaired CBS activity.
PCC is a mitochondrial enzyme comprised of non-identical subunits
encoded on different chromosomes. Deficiency of PCC causes propionic
acidemia. This condition is an autosomal recessive trait that is often
life threatening in neonates. Recent research has indicated that in
certain populations the incidence of this disease is far higher than
previous estimates. Our research in this area is focused on improving
our understanding of the molecular mechanisms that underlie the highly
variable correlation between genotype and phenotype in propionic acidemia.
To this end, we have developed a recombinant expression system using
molecular chaperones that allows us to assess the effects of specific
mutations upon PCC function. Adaptation of this system for large-scale
expression of the human PCC holoenzyme in E.coli will facilitate characterization
of the PCC enzyme complex using both spectroscopic and X-ray diffraction
studies. We are currently identifying the promoter regions of both
PCC genes to elucidate how PCC activity is regulated and to perform
a functional analysis of the sequences that determine basal promoter
activity in the human PCC genes. Techniques employed include the use
of reporter constructs in luciferase assays, site directed mutagenesis,
mammalian tissue culture, immunohistochemistry, band shift analysis
and DNA footprinting.
Further information on our research can be found at http://www.uchsc.edu/sm/cbs
.
Selected Publications
Kraus JP, Oliveriusova J, Sokolova J, Kraus E, Vlcek C, de Franchis R, Maclean KN, Bao L, Bukovska G, Patterson D, Paces V, Ansorge W, Kozich V (1998) The human cystathionine b-synthase (CBS) gene: complete sequence, alternative splicing and polymorphisms. Genomics 52:312-324
Meier M, Janosik M, Kery V, Kraus JP, Burkhard P (2001) Structure of human cystathionine beta-synthase: a unique pyridoxal 5'-phosphate-dependent heme protein. EMBO J 20:3910-3916
Mudd SH, Levy HL, Kraus JP (2001) Disorders of transsulfuration. In: Scriver CR, Beaudet AL, Sly WS, Valle D, Childs B, Kinzler K, Vogelstein B (eds) The Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill, New York, pp 2007-2056
Kelson TL, Ohura T, Kraus JP (1996) Chaperonin-mediated assembly of wild
type and mutant subunits of human propionyl-CoA carboxylase expressed
in Escherichia coli. Human Molecular Genetics 5:331-33
Miles EW, Kraus JP (2004) Cystathionine beta-synthase: structure, function,
regulation, and location of homocystinuria-causing mutations. J Biol Chem
279:29871-29874
