Unit 4 - Lec 14

Question 1

when did LUCA appear?

Answer 1

4 bya

Question 2

what is LUCA?

Answer 2

thermophilic

Question 3

what are hyperthermophiles mostly?

Answer 3

mostly Archaea

Question 4

what can bacteria also be?

Answer 4

hyperthermophilic

Question 5

what is the superheated vent water?

Answer 5

sterile- no microogranisms
- no biochemical markers that signal life

Question 6

who is the record holder for temp?

Answer 6

methanopyrus

Question 7

what happens at 150C?

Answer 7

• ATP degrades
• life forms have to deal with heat liability of a molecule that is universally distributed in cells

Question 8

how to maintain stabilitity of DNA/RNA and proteins at higher temps?

Answer 8

• thermostable proteins
• thermosomes
• chaperonins
• reverse DNA gyrase
• RNA modification

Question 9

thermosome function?

Answer 9

• keeps other proteins properly folded and functional at high temps
• maintains DNA

Question 10

what happens after heat shock treatment?

Answer 10

sufficient to enable cells to keep growing and dividing

Question 11

thermostable proteins

Answer 11

• specific folding
• not specific amino acids
• alpha helical structure in thermostable proteins
• very hydrophobic core - can’t easily fold
• high ionic interactions on surface - can’t easily fold

Question 12

chaperonins

Answer 12

heat shock proteins
- help refold partially denatured proteins

Question 13

DNA/RNA involved thermostability

Answer 13

• increased K+
• reverse DNA gyrase
• reverse gyrase introduces positive supercoils into DNA
• pos supercoiling stabilizes DNA
• highly basic DNA-binding proteins
• heat resistant lipids

Question 14

ribosomal RNAs

Answer 14

• structural and functional components of ribosome- cell’s protein synthesizing apparatus
• small ribosomal subunit in hyperthermophiles has 15% greater proportion of GC base pairs

Question 15

what does higher GC content of ribosomal RNA confer?

Answer 15

greater thermal stability

Question 16

GC content of genomic DNA of hyperthermophiles is often _____

Answer 16

low

Question 17

hypothesis for hyperthermophilic archaea, h2, microbial evolution

Answer 17

• biological molecules, biochemical processes and first cells arose on Earth around hydrothermal springs and vents on sea floor
• phylogeny of modern thermophiles suggests that they may be closest remaining descendants of ancient cells

Question 18

what does the oxidation of H2 link to?

Answer 18

reduction of Fe3+, S^0, NO3- and sometimes O2

Question 19

what is commonly spread in hyperthermophiles and why?

Answer 19

use of H2
H2 was available and there was many suitable inorganic e acceptors in primordial enviro
- metabolism evolved in primitive organisms

Question 20

where do chemolithotrophic organisms live?

Answer 20

hottest temp possible
- 110C

Question 21

what is the least heat-tolerant of all bioenergetic processes?

Answer 21

photosynthesis
- no hyperthermophilic representatives

Question 22

hydrogen-metabolizing bacteria

Answer 22

H2 is sole e donor
O2 is e acceptor
fix CO2
hydrogenase enzyme
microaerophilic
Ni2+ must be present
some fix N2

Question 23

what do diverse aerobic bacteria use?

Answer 23

atmospheric H2 for growth and survival

Question 24

H2 oxidation

Answer 24

• globally significant process
• regulates composition of atmosphere
• enhances soil biodiversity
• drives primary production in extreme enviro

Question 25

atmospheric H2 oxidation

Answer 25

- uncharacterized members of Ni-Fe hydrogenase superfamily

Question 26

what conditions are unsuitable for enzymes?

Answer 26

very low level H2 and O2

Question 27

NiFe hydrogenase

Answer 27

membrane bound H2 oxidizing metalloenzymes low affinity to H2 no support oxidation of atmospheric H2 O2 poisoning problem

Question 28

what are high affinity lineage NiFe hydrogenases?

Answer 28

capable to transfer electrons derived from atmospheric H2 oxidation to ETC

Question 29

what are newly discovered enzymes?

Answer 29

significantly higher affinity for H2 and are insensitive to inhibition by O2

Question 30

Ginter et al.

Answer 30

determined cryo-electron microscopy structure of hydrogenase Huc from Mycobacterium smegmatis

Question 31

Huc

Answer 31

- enzyme that oxidizes atmospheric H2 - O2 tolerant hydrogenase - multiple metal clusters - highly stable at room temp with melting temp 78.3C - oxidize atmospheric H2 below levels of detection in chromatography - gas channels provide entrance for H2 (road to active site)

Question 32

was O2-tolerant hydrogenase from E.coli Hyd1 able to tolerate high O2 levels?

Answer 32

no

Question 33

structural basis for energy extraction from H2

Answer 33

four-lead clover associated with membrane vesicles via stalk-like protrusion cellular membrane activity mainly associated with soluble fraction

Question 34

where are bottlenecks?

Answer 34

between active site and enzyme surface - H2 enters active site - O2 excluded by bottlenecks - O2 not getting close to active site

Question 35

what is the critical point in O2-insensitivity?

Answer 35

bottleneck after three gas tunnels that precedes active site