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Molecular Structure and Biosynthesis of the Fatty Acid Synthetase-Multienzyme Complex of Yeast.

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C O N F E R E N C E REPORTS
Kinetic Investigations of Anodic Oxide
Layers on Niobium and Tantalum
vacancies in anodic oxides of tantalum and niobium are
described by the same mechanism.
Lecture at Kiel on December 7, 1972 [VB 363 IE]
German version: Angew. Chem. 85. 31 1 (1973)
By K . E. Heusler[']
Non-poroys oxide layers of uniform thicknesses between
about 50A and 0.5pm can be deposited on niobium or
tantalum by anodic oxidation in electrolyte solutions. The
glass-like oxides have the composition M,O,( -x). The
oxygen deficiency creates oxygen vacancies whose concentration may approach several percent of the oxygen sites
available.
[I] D. Stiirilr and K. E. Heusler, 2. Phys Chem., N. F. 65. 201 (1969).
[2] P. Schufze and K . E. Heusler, unpublished
[3] K. E. Hrusler and P. Schliiter, Werkst. Korros. 20, 195 (1969); 2.
Phys. Chem., N. F. 69, 140 (1970); P Schiuter. Dissertation, Universitlt
Stuttgart 1971.
[4] G . Sauerbrey, 2. Phys. 155, 206 (1959).
The concentration of vacancies is increased by dissolution
of oxygen from the oxide into the underlying metal and
is decreased by reaction of the vacancies with molecular
oxygen. Below 400°C these reactions d o not alter the
thickness of the layer or its crystallinity.
MolecularStructure and Biosynthesisof the Fatty
Acid Synthetase-MultienzymeComplex of Y east
When studying these reactions, the fact that the anodic
oxides on niobium and tantalum are impurity semiconducwhose electronic conductivity is a measure of
the concentration of oxygen vacancies, was utilized. The
electronic conductivity of oxide layers on niobium measured at a constant temperature increases by up to nine
powers of ten during heat treatment in vacuum for several
hours at temperatures between 100 and 250°C. This effect
is partly due to an increase of the concentration of vacancies. There is also a substantial contribution from the
lowering of the activation energy of electronic conductivity
with increasing concentration of vacancies. However, the
activation energy remains constant in certain ranges of
concentration. There the experiments show the concentration of vacancies to rise at a constant rate. The rate-determining step is the transfer of oxygen atoms through the
interface from the oxide into the metalr3].
The reaction of oxygen vacancies in niobium oxide with
oxygen is also determined by the phase-boundary reaction.
Its rate is proportional to the oxygen pressure and to
the square of the vacancy Concentration. The mechanism
suggested is that in a first, rapid step an oxygen molecule
occupies a vacancy on the surface and that two normal
oxygen ions are formed in a second, slow step by reaction
of a second vacancy with the intermediate, involving
cleavage of the oxygen-oxygen bond.
The reaction between oxygen vacancies in anodic tantalum
oxide and oxygen was investigated with a quartz frequency
balance[2! The frequency of a quartz oscillator decreases
linearly with the mass per unit areal4]. The quartz crystals
were coated on both sides by anodized tantalum layers.
The accuracy of the measurements was about
g
cm- d - I . Vacancies were generated by heating the sample
in uucuo. The kinetics of the increase of mass observed
after exposure to oxygen is typical of a reaction whose
rate is determined by the phase-boundary reaction at low
oxygen pressures and short times, but by diffusion of vacancies toward the surface of the oxide at high oxygen pressures
and long times. The rate of the phase-boundary reaction
is proportional to the oxygen pressure. The dependence
of the rate on the concentration of vacancies also supports
the view that the reactions of the oxygen with oxygen
__
[*] Prof. Dr. K. E. Heusler
Selbstandige Abteiiung Korrosion der
Technischen Universitat Clausthal
3392 Clausthal-Zellerfeld, Robert-Koch-Strasse 42 (Germany)
A n y e n . Chenr. infurnot. Edit. 1 Vol. I2 ( I Y 7 3 1
,
No. 4
By Eckhurt Schweizer"'
The fatty acid synthetase complex of the yeast Succhuromyces cereuisiue is coded by two unlinked, complex gene
~.
f u s l could be localized
loci, fusl and f u ~ 2 [ ' . ~Whereas
on chromosome XI of the revised gene map of yeast (formerly chromosome fragment 5), the position of fus2 is
so far
Genetically and biochemically pleiotropic mutants of both
fus-gene loci are known[']. As a rule, they d o not synthesize
material (CRM) that cross-reacts immunologically with
specific fatty acid synthetase antiserum. Synthetase-analogous CRM is, however, formed in uitro when cell extracts
of suitable CRM-negative, pleiotropic fus-rnutants are
mixed. This in v i f r o complementation indicates that the
twofus-gene loci are read off independently of one another,
and shows further that the native, biologically active conformation of these components are formed only on their
association to the total complex. This explains the hitherto
unsuccessful attempts to dissociate the complex into enzymatically active partial enzymes.
By feeding radioactive pantothenic acid to various ,fu.smutants it could be shown that in fusZ one of the two
gene regions responsible for the condensation reaction
obviously controls the synthesis of the acyl carrier protein.
Mutants of this region contain a pantothein-free fatty acid
synthetase complex, which in v i m lacks only the condensation reaction.
SDS-polyacrylamide gel electrophoresis permits separation of the fatty acid synthetase complex into two components differing slightly in molecular weight (170000 to
19oOOO). In some mutants one of these two protein bands
can be shifted to a different position corresponding to
a lower molecular weight. It is thus unlikely that these
two bands represent two groups of proteins, each containing different components of the same molecular weight.
Rather, the experiments indicate that the two gene loci
fusl and fus2 each code for a single but polyfunctional
peptide chain. Individually, the two chains are obviously
enzymatically inactive but on association to the complex
undergo a conformational change forming the active sites
of the partial enzymes. This association perhaps also yields
the active sites of the three acyl transferases for which
no individual structural genes have yet been identified.
[*] Prof. Dr. E. Schweizer
Instilut fur Biochemie der Universitlt
87 Wurzburg, Rontgenring 11 (Germany)
341
C'ontrary to the structure of bacterial multienzyme complexes, it is probable that multifunctional peptide chains
participate in thestructureofa series of eukaryotic multienzyme complexes. According to this concept, during the
coursc of evolution an increasing functional structuring
of thc cell interior would lead not only 10 formation of
multienzyme complexes but also to complexes with multifunctional pcptide chains. It is clear that their biosynthesis
is favored. both kinetically (by abolition of association)
and by regulation (no stoichiometric problem). over the
association of the individuzl partial enzymes.
Lecture at Karlsruhe o n ldnuary 18. 1973 LVB 364 IF.]
(ierrnan version' Angeu. Chum. H 5 . 365 ( I Y 7 i i
[ I ] E S i l r u i ' i ~ L~ ~ Kuhil.
.
and H Cmiorpli. Iloppe-Suylers Z. P h y s l ~ l
C'hcni. 352. i 7 7 I 19711.
[-'I L K r I h . I I ('ocrorph. m d & . % I n ~ v i x r . C u r d . Blochcm. ?4. 492
11972).
131 G Brwll. H . ('u\rorpli. .ind E S0rwi:tv.
prers
Molec. Gen, (ienet.. ~n
ABSTRACTS
-
phous Catalysts. Catal. Rev. 6, 293-322
ferences]
(1972); 45 reLRd 561 IE---GI
Enzymes insolubilized on inorganic supports are surveyed
by H . 11. Weetall and R . A . Messing. Enzyme derivatives
that are insoluble in water have the advantage that they
can be used as columns or suspensions and can readily be
added to, or removed from, reaction mixtures. Moreover,
they can be used repeatedly. Such derivatives are obtained
by adsorption or covalent binding of enzymes onto supports. The article describes the available methods, lists the
supports used, and considers the properties of some of the
resulting preparations. [Insolubilized Enzymes on Inorganic Materials. Chem. Hiosurfaces 2, 563-595 (1972);
101 references]
[Rd 549 1E 4 1
Interactions between normal and malignant cells are the
subject ofa review by L. Weiss. It describes the nature of the
surface of the cell and the events occurring on cel!ular
contact and subsequently on the surface and in the interior
of cells. Interactions with malignant cells are then considered which appear to be responsible for the phenomenon of
metastasis,on the one hand,and for tumor resistance, thanks
to the destruction of malignant cells by the lymphocytes
of the host organism, on the other. [Interactions between
Normal and Malignant Cells. Chem. Biosurfaces 2,
3 7 7 4 7 (1972); 371 references]
[Rd 557 IE--GI
The use of X-ray analysis in studies on amorphous catalysis
is surveyed by P. Rurnu.sur)ij and A . J . Lui,i7u,d. Numerous
industrial catalysts (SiO,,AI20,,SiO2/A1,O,~,ultramarines
are considered in the present article) possess a large surface
area and a high porosity, but are not crystalline and therefore give diffuse X-ray diagrams. However, with the aid of
two complementary methods, even such diagrams can
provide information about atomic distances and coordination numbers. The methods are described, and the reader
is provided with indications regarding experimental techniques. [X-Ray Scattering Techniques in the Study of Amor-
342
The role of solvated electrom in electrode processes is dealt
with in a review by B. E. Conway. Solvated electrons can
be formed by photoinjection from the cathode under certain
irradiation conditions, by direct injection from the cathode
if a suficiently large potential difference is present at the
interface between cathode and solution, and by dissolution
of basic metals in solvents such as ammonia and some
amines. The article treats experimental proofs of the
occurrence of solvated electrons as intermediates in cathodic and photocathodic processes in various media. The
electroorganic chemistry of reductions with solvated electrons is considered only in so far as it provides an indication
of cathodic production of solvated electrons. [Solvated
Electrons in Field and Photo-Assisted Processes at Electrodes. Mod. Aspects Electrochem. 7. 83-142 (1972);
118 references]
[Rd 563 IE--GI
The IR spectroscopy of nucleic acids is the subject of a
review authored by G . P . Zhizhina and E . F . O/ciriik. The
article contains IR and Raman data for DNA and R N A
as well as their components and deals with the assignment
of IR bands to individual bond vibrations. An approach
to the theoretical treatment of the normal vibration of
the nucleic acid skeleton is described. The authors show
how IR provides information about the interactions of
heterocyclic bases and about the secondary structures of
nucleic acids. as well as their interactions with proteins.
metal ions, and a few biologically active substances.
[Infrared Spectroscopy of Nuc!eic Acids. Russ. Chem. Rev.
41. 258--280 ( 1972); 2 18 references]
[Rd 589 IE-Q]
The reactivity of cyclic organic phosphorus compounds is
reviewed by K. F . Hudson and C. Broivn. The review is
based on considerations of the rules of pseudorotation
and on the postulates that ring strain decreases a) in the
reaction of cyclic phosphoryl or phosphonium compounds
with nucleophiles. and b) in the reaction of cyclic P"'
compounds with nucleophiles to give pentacoordinated
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acid, multienzyme, structure, complex, molecular, yeast, fatty, synthetase, biosynthesis
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