Charlotte S. Russell
Professor
Biochemistry
Tel. (212) 650-6681
Fax: (212) 650-6657
Office: Science Building-J1337
Labs: Science Building-J1303, 1321
E-mail: chrcc[at]sci.ccny.cuny.edu
B.A., Brooklyn College
M.A., Ph.D. Columbia University
Research
I.Tetrapyrrole biosynthesis in Escherichia coli
Heme is a tetrapyrrole which is bound to iron and which is the prosthetic
group of the hemoglobins, cytochromes, catalase and peroxidases. Other
tetrapyrroles found in nature include chlorophylls (tetrapyrrole bound to
magnesium), Vitamin B12 (tetrapyrrole bound to cobalt) and Factor 430
(tetrapyrrole bound to nickel). These tetrapyrroles have a very
highly-conserved biosynthetic pathway.
In collaboration with Prof. Sharon Cosloy, we have been studying heme and
siroheme biosynthesis and its regulation in Escherichia coli. We are
using the tools of biochemistry and molecular biology for this purpose. We
showed that the first committed intermediate in tetrapyrrole biosynthesis,
5-aminolevulinic acid (ALA), is made from glutamate (C5 pathway) in E.
coli. The source of ALA in eukaryotes, except for green plants, is glycine
and succinyl CoA (C4 pathway).
(1) We isolated and characterized heme-permeable strains of E. coli
which also had mutations in structural genes for enzymes involved in the
biosynthetic pathway. These strains were exploited for complementation
studies.
(2) We cloned hemA by complementation of a hemA- hemin-permeable
mutant and showed that it was essential for ALA synthesis. The nucleotide
sequence showed no homology to any known hemA of the C4 pathway.
Subsequent studies with isotopically-labelled precursors revealed that E.
coli makes ALA by the C5 pathway, in the same way as green plants. E.
coli became a powerful tool for studying ALA synthesis and cloning genes
of the C5 pathway from many sources. This work led to the realization
that almost all bacteria and archaea use the C5 pathway for tetrapyrrole
synthesis.
(3) We cloned and sequenced hemB and showed that the gene product of
hemC, porphobilinogen deaminase (PBG-D), requires an active hemB for
activity. hemB codes for ALA dehydratase which synthesizes the "coenzyme"
for PBG-D.
(4) We overexpressed hemA to acquire enough of its gene product,
glutamyl-tRNA reductase (GTR) for study. Of the three steps leading from
glutamate to ALA, it is widely-believed that the GTR step regulates ALA
synthesis. Many experiments show that ALA concentration controls the whole
pathway to heme.
(5) Biochemical experiments showed that GTR is inhibited by heme and
stimulated by tRNA(glu); the latter presumably because of its role as part
of the substrate of GTR.
(6) When various parts of the 5' upstream region of hemA were cloned
in front of a reporter gene, it was found that hemA transcription is
regulated by the transcriptional reulators, ArcA and FNR. It is inhibited
by glucose and this inhibition is mediated by cAMP-CRP. Starvation for ALA
or heme stimulates transcription.
(7) hemE, the structural gene for uroporphyrinogen decarboxylase, the
first enzyme after the pathway diverges to make heme or siroheme, was
cloned and sequenced. Using construct with various parts of the upstream
region of the gene, it was shown that hemE is the first gene of an operon.
As a consequence of the results obtained above, we are engaged in the
following work:
(8) Several putative regulatory mutants in heme biosynthesis have been
isolated and characterized. These strains accumulate intermediates of the
tetrapyrrole biosynthesis pathway but do not require heme for growth. The
mutations in these strains are being mapped and identified.
(9) The 5'upstream region of hemA has various structural features
which are enigmatic. Experiments are under way to determine the functions
of these features in the expression of hemA.
(10) Experiments are underway to study the interactions of GTR with
glutamyl-tRNA and glutamyl-tRNA synthetase.
II. Lipid-mediated Hemagglutination
We have reported that some oxidation and "aging" products of oleic
acid agglutinate some species of red cells. By using model compounds, we
concluded that oligomeric C18 fatty acids are responsible for this
activity. We are studying the aggregation characterisiics of these
oligomers. This work is relevant to the properties of lipids in heated and
processed food and in changes associated with aging.
Recent Publications
Heating unsaturated fatty acids in air produces hemagglutinins, Ioannis S.
Patrikios, O'Neil Britton, Darryl K. Bing and C.
S. Russell, Biochim. Biophys. Acta, 1212, 225-234 (1994).
5-Aminolevulinic Acid Synthesis in Escherichia coli Requires Expression of
hemA, Wei Chen, C. S. Russell, Y. Murooka
and S. D. Cosloy, J. Bacteriol., 176, 2743-2746 (1994).
Characterization of a hemA/hemE mutant of E. coli and regulation of hemE,
Susan Pido, K. W. Tsoi, H. Umanoff,Sharon D. Cosloy and C. S. Russell,
Cell. and Molec. Biol., 40, 945-956 (1994).
Expression of glutamyl-tRNA reductase in Escherichia coli., W. Chen,
Lavern Wright, Simon Li, S. D. Cosloy & C. S. Russell, Biochim. Biophys.
Acta, 1309, 109-121 (1996)
"Lectures and Recitations" in Before the Class: Handbook for the Novice
Instructor, published by CUNY Graduate center, New York, NY, 1997