Comparisons of microtubule
behavior between species point to differences that raise questions
about the biological importance of dynamic instability.
Notothenioid fish, for example, which live in the Southern Ocean at
a constant temperature of –1.8°C, have remarkably stable
microtubules compared with warm-blooded vertebrates such as the
cow. This is an essential modification for notothenioid fish
because normal microtubules disassemble completely into αβ-tubulin
dimers at 0°C. Measurements on individual microtubules in solutions
of pure tubulin show that notothenioid fish microtubules grow at a
much slower rate, shrink at a much slower rate, and only rarely
switch from growth to shrinkage (catastrophe) or from shrinkage to
growth (rescue) (Table 1).
A. The amino acid sequences of the α- and β-tubulin subunits from notothenioid fish differ from those of the cow at positions and in ways that might reasonably be expected to stabilize the microtubule, in accord with the data in Table 16–1. Would you expect these changes to strengthen the interactions between the α- and β-tubulin subunits in the αβ-dimer, between adjacent dimers in the protofilament, or between tubulin subunits in adjacent protofilaments? Explain your reasoning.
B. Dynamic instability is thought to play a fundamental role in the rapid microtubule rearrangements that occur in cells. How do you suppose cells in these notothenioid fishes manage to alter their microtubule architecture quickly enough to accomplish essential cell functions? Or do you suppose that these cells exist with a stable microtubule cytoskeleton that only slowly rearranges itself?
A. In a microtubule lateral and longitudinal interaction between the tubulin subunits are responsible for making the tubular form . Longitudinal contracts between the ends of adjacent subunits link the subunit of head to tail into a linear protofilament.
B. The dynamic instability of microtubules free of microtubules associated proteins from two genera of cold living fishes. Critical for polymerization of fish tubulin were in the neighborhood of 1mg/ml . Rate of elongation and frequencies of growth to shorting transition of fish microtubules were significantly smaller than therefore mammalian microtubules.
Comparisons of microtubule behavior between species point to differences that raise questions abo...
1) Comparisons of microtubule behavior between species point to
differences that raise questions about the biological importance of
dynamic instability. Notothenioid fish, for example, which live in
the Southern Ocean at a constant temperature of –1.8°C, have
remarkably stable microtubules compared with warm-blooded
vertebrates such as the cow. This is an essential modification for
notothenioid fish because normal microtubules disassemble
completely into αβ-tubulin dimers at 0°C. Measurements on
individual microtubules in solutions of pure tubulin show that
notothenioid fish microtubules...
10. Write a one-page summary of the attached paper? INTRODUCTION Many problems can develop in activated sludge operation that adversely affect effluent quality with origins in the engineering, hydraulic and microbiological components of the process. The real "heart" of the activated sludge system is the development and maintenance of a mixed microbial culture (activated sludge) that treats wastewater and which can be managed. One definition of a wastewater treatment plant operator is a "bug farmer", one who controls the aeration...