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Biol 4890 > Chapter 30 > Flashcards

Chapter 30 Flashcards

1
Q

Protein is synthesized from ? to ? end

A

N to C

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2
Q

mRNA is decoded in ? to ? direction

A

5 to 3

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3
Q

linking of AA to tRNA by ? is driven by ATP

A

aminoacyl-tRNA synthetase

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4
Q

Two subunits of ribosome

A

30S and 50S

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5
Q

? AAs are incorporated / second

A

20

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6
Q

one mistake in every ? AAs

A

10000

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7
Q

base modifications stabilize ? of tRNAs and provide additional contacts to ?

A

tertiary structure. contacts to protein factors

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8
Q

common features of all tRNA

A

cloverleaf secondary structure. 5 regions w/o complementary base pairing. anticodon and AA acceptor site at opposite ends

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9
Q

activation of AAs for tRNA attachment

A

AA + ATP&raquo_space; Aminoacyl adenylate + PPi. driven by PPi hydrolysis

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10
Q

activation and charging reactions catalyzed by ?

A

tRNA synthetases

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11
Q

class one aminoacyl-tRNA synthetases acylate ?

A

2’-OH

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12
Q

class two aminoacyl-tRNA synthetases acylate ?

A

3’-OH

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13
Q

threonyl-tRNA synthetase uses ? to coordinate with -OH group of threonine to allow it to recognize threonine with an accuracy of ?

A

Zn ion. 99%

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14
Q

? allows 99.99? accuracy by threonyl-tRNA synthetase

A

proofreading

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15
Q

tRNA synthetase two active sites

A

activation site for charging and editing site the hydrolyzes incorrectly charged tRNAs

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16
Q

crucial step in converting from a nucleic acid code to a protein one

A

tRNA synthetases recognizing cognate tRNAs

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17
Q

50S subunit composed of ?

A

34 proteins, 23S and 5S rRNAs

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18
Q

30S subunit composed of ?

A

21 proteins and 16S rRNA

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19
Q

initiation of protein synthesis

A

30S subuint binds mRNA and a specific initiator tRNA

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20
Q

elongation of protein

A

50S subunit attaches to complex and polypeptide syntehsis begins

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21
Q

termination of protein synthesis

A

release factors bind at stop sequences to release polypeptide and disassemble ribosomes

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22
Q

initiator tRNA

A

a methionyl-tRNA that has been formylated. fMet-tRNA. Has peptide bond

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23
Q

start of protein synthesis is determined by?

A

pairing of mRNA bases w/ 3’ end of 16S rRNA. pairing of initiator codon on mRNA w/ anticodon of an initiator tRNA

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24
Q

binding of fMet-tRNA

A

30S ribosome subunit combines with initiation factors IF1-IF3 to facilitate binding and prevent premature association with 50S subunit

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25
Q

formation of quaternary complex

A

IF1 and IF3 dissociate. IF2 hydrolyzes GTP to drive release which allows 50S to bind

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26
Q

EPA sites

A

E: uncharged site. P: peptidyl site. A: aminoacyl site

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27
Q

elongation cycle

A

aninoacyl-tRNA binding > peptide bond formation > GTP hyrolysis by EF-G drives translocation > tRNA dissociation

28
Q

aminoacyl-tRNAs are delivered to A site by ?

A

elongation factor Tu (EF-Tu) complexed with GTP

29
Q

EF-Tu*GDP is recharged with GTP by ?

A

guanine nucleotide exchange factor of EF-Ts

30
Q

peptidyl transferase reaction is catalyzed by ?

A

rRNA in 50S subunit

31
Q

modification of a charged tRNA leads to ?. This is used in vitro to synthesize proteins containing ?

A

incorrect incorporation. unnatural amino acids

32
Q

wobble position

A

5’ end (first base) of anticodon and 3’ end (third base) of codon are less discriminating

33
Q

Inosine in first base of anticodon can bind with ? on third base of codon

A

U, C, A

34
Q

yeast ala-tRNA contains ? in the anticodon

A

inosine

35
Q

how does the ribosome read the first two codns so accurately?

A

rRNA makes specific contacts on the minor groove of the codon-anticodon helix

36
Q

termination of translation

A

protein release factors that mimic tRNAs recognize and bind stop codons to release peptide from complex

37
Q

STOP codons

A

UAA, UAG, UGA

38
Q

release factors activate a ? to hydrolyze the peptidyl-tRNA

A

water molecule

39
Q

RF-1

A

pairs with UAA or UAG

40
Q

RF-2

A

pairs with UGA

41
Q

RF3

A

causes dissociation of ribosome, mRNA and release factors

42
Q

? powers conformational change in the ribosome

A

GTP

43
Q

? (4) are all part of the g-protein superfamily and interact with the same site on the 50S subunit

A

IF-2, EF-Tu, EF-G, RF-3

44
Q

Polysomes

A

on average about 10 ribosomes are attached to each mRNA

45
Q

monocistronic

A

circularized mRNAs that encode for only one protein. found only in eucaryotes

46
Q

30S and 50S ribosome subunits combine to form a ? subunit in procaryotes

A

70S

47
Q

40S and 60S ribosome subunits combine to form a ? subunit in eucaryotes

A

80S

48
Q

In eucaryote initiation, ? (3) associate in a ternary complex

A

eIF-2, GTP, Met-tRNA

49
Q

in eucaryote initiation, ternary complex binds to ? complex to from ? complex

A

40S ribosomal subunit/eIF complex to form 43S preinitiation complex

50
Q

in eucaryote initiation, ? and ? add to 43S complex forming the 48S complex

A

mRNA and eIF4

51
Q

in eucaryote initiation, 48S initiation complex scans for ? with the help of ?

A

AUG start codon with the help of helicases

52
Q

in eucaryote initiation, when 48S complex meets AUG, ? is hydrolyzed and ? adds to make 80S complex

A

GTP. 60S

53
Q

eucaryotic mRNAs are unique because?

A

7-methyl-G cap at 5’ end. Poly(A) tail at 3’ end

54
Q

5’ cap is recognized by ?

A

eIF-4E

55
Q

PolyA tail is recognized by ?

A

pabp1

56
Q

eIF-4E and pabp1 both bind to ?

A

eIF-4G

57
Q

? proteins recognize both ends of mRNA to circularize, protect, and compact

A

eIF-4 group

58
Q

some eIF-4 group proteins and S6 are activated by ?

A

phosphorylation

59
Q

phosphorylated eIF-2 binds so tightly to eIF-sB that ?

A

guanine nucleotide exchange is blocked and translation cannot initiate

60
Q

IRES

A

internal ribosome entry sites. able to translate without 5’caps and 3’ tails. Includes polio virus and eIF-4G

61
Q

why is termination simpler in eucaryotes

A

only one release factor that hydrolyzes GTP at stop codon

62
Q

proteins are synthesized as precursors with ? sequence that is subsequently removed. Purpose?

A

N-terminal. Tags to send to correct place in cell.

63
Q

SRP

A

signal recognition particle. binds weakly to all ribosomes but tightly to ribosomes translating signal peptides. stops translation by blocking elongation factor binding site. targets ribosome to ER where SRP interacts with SRP receptor. SRP and receptor hydrolyze GTP and dissociate.

64
Q

streptomycin function

A

inhibit translation initiation and cause misreading of mRNA

65
Q

puromycin function

A

causes premature translation chain termination by acting as aminoacyl-tRNA analog

Biol 4890 (16 decks)

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