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Flashcards in Final 2 Deck (105):
1

Where do proteins without a sorting signal end up?

Stay in cytosol

2

Gated transport of the nucleus through what?

Nuclear pore complexes

3

3 types of intracellular transport

Gated, transmembrane, vesicular

4

2 types of sorting signals

Signal sequences, signal patches

5

How long are sorting signals?

15-60 continuous residues

6

How are signal sequences removed from a protein?

Signal pepidases

7

Proteins that make up a NPC

Nucleoporins

8

About how many NPCs does a mammalian cell contain?

3000-4000

9

True or false: nuclear proteins can be transported through a pore complex while folded

True

10

Binding sites for nuclear import receptors

F-G repeats

11

Provides energy for concentration of particular proteins on one side of the nuclear envelope

Ran

12

What kind of molecule is Ran

GTPase

13

Triggers hydrolysis of ATP, converting Ran-GTP to Ran-GDP in the cytosol

GAP (GTPase-activating protein)

14

Promotes the exchange of GDP for GTP, converting Ran-GDP to Ran-GTP

GEF (Guanine exchange factor)

15

Ran-____ is primarily in the cytosol; Ran-____ is primarily inside the nucleus

GDP, GTP

16

Where are mitochondrial signal sequences?

Amino-terminus

17

Completes mitchondrial import by repeated cycles of ATP hydrolysis

HSP70

18

Helps insert membrane proteins into outer membrane

TOM (translocase of outer membrane)

19

Spans both mitochondrial membranes and mediates translocation of proteins in to the matrix space

TIm23

20

Mediates the insertion of a subclass of inner membrane proteins

TIM22

21

Mediates the insertion of inner membrane proteins synthesized in the mitochondrial matrix

OXA complex

22

Keeps mitochondrial precursors in their unfolded confromation using ATP

HSP70

23

What acts as a stop-transfer sequences that prevents further translocation across IMM

Hydrophobic signal

24

True or false: all peroxisome proteins must be imported from the cytosol

True

25

House oxidative enzymes such as oxidases that produce peroxide

Peroxisomes

26

How are peroxisomes inolved in lipid metabolism?

Degrade fatty acids by beta oxidation

27

True or false: proteins imported into peroxisomes can be imported fully-folded

True

28

Proteins involved in the generation or maintenace of peroxisomes

Peroxins

29

helps insert and fold beta-barrels in the OMM

SAM

30

Protein that binds to emergent signal sequences, halts translation, and targets the complex to the ER

Signal recognition particle (SRP)

31

How are SRPs recognized on the ER membrane?

SRP receptor

32

Protein translocation channel of the ER

Sec61 complex

33

ER chaperone that binds and releases proteins to maintain directionality

BiP

34

Protease that removes signal sequences in the ER membrane

Signal peptidase

35

-COOH-terminus in the cytoplasm

Type I membrane protein

36

-NH3-terminus in the cytoplasm

Type II membrane protein

37

What protein charges typically remain in the cytosol?

Positive

38

An ER lumenal Hsp70 homolog that binds to unfolded proteins and prevents aggregation

BiP

39

Calcium-binding proteins that are lectins that bind to oligosaccharides on incompletely folded proteins and prevents aggregation

Calnexin, calreticulin

40

Enzyme that aids in folding by helping correct disulfide bond formation in newly synthesized proteins

Protein disulfide isomerase (PDI)

41

Covalent addition of sugars to proteins

Glycosylation

42

Attachment of sugar to the hydroxyl group of serine on threonine

O-linked glycosylation

43

Attachment of sugar ot the amide nitrogen of asparagine

N-linked glycoslyation

44

Enzyme that transfers an oligosaccharide to the Asn residue

Oligosaccharyl transferase (OST)

45

Lipid scaffold that helps transfer sugars to proteins

Dolichol

46

Why are sugars added to proteins in the ER

As a tag to mark the state of protein folding

47

ER resident enymze that removes glucose in order to allow a protein to continue folding

Glucosidase

48

Adds a single terminal glucose to a protein that is not properly folded

Glucosyl transferase

49

Cytoslic degradation machinery

Proteasome

50

ER resident protein sequence

HDEL or KDEL

51

Protein coat used for Golgi -> PM and endocytosis

Clathrin

52

Protein coast used for intragolgi and retrograde Golgi -> ER

COPI

53

Protein coat for ER -> Golgi

COPII

54

Coat subunit that has enzymatic activity for COPI

ARF

55

Coat subunit that has enzymatic acitivty for COPII

SAR1

56

Stimulate GTPase activity and make it go faster

GAP (GTPase activating protein)

57

Molecule that initiates the formation of vescile budding on the ER membrane

SAR1

58

When SAR1 is off, where is its helix?

Tucked away

59

When SAR1 is on, where is its helix?

Exposed and inserted into phopholipid bilayer

60

How does SAR1 initiate budding?

Nucleates the binding of coat proteins

61

Two dimeric subunits of COPII coat

Sec23/Sec24

62

Interacts with integral membrane proteins that aids in the selection of membrane integral cargo receptors

Sec24

63

Forms a cage structure to deform the membrane and form a vesicle

Sec13/Sec31

64

What happens when SAR1 cleaves its GTP to GDP?

Leaves coated vesicle, starting a cascade that uncoats the vesicle

65

2 addressing systems for vesicles

Tethering, docking

66

How many proteins are in the complex involved in the tethering process?

5-10

67

Protein that mediates the communication between a vesicle and a membrane

Rab proteins

68

What kind of protein are Rab proteins?

G-protein

69

What does a Rab protein do exactly?

Tells SNARE proteins that a vesicle has been "tethered" and now able to "dock"

70

Responsible for the merger of two phospholipid bilayers

SNARE proteins

71

2 proteins involved in recycling SNARE proteins

Adapter SNAP and chaperone NSF

72

Forward traffic

Anterograde

73

Backwards traffic

Retrograde

74

How is the localization of the golgi in perinuclear region maintained?

Microtubules

75

Some proteins getting packaged into ER vesicles just because they are in the right place at the right time

Bulk Flow

76

How are ER resident proteins stopped from being packaged into vesicles for transport?

Aggregate themselves into too large of complexes for vesicles

77

Aggregation of ER proteins

Kin Recognition

78

Fusion of uncoated vesicles in between ER and cis-Golgi

Vesicular tubular clusters (VTC)

79

True or false: VTCs are unique to ER to golgi transport

True

80

Fusion of vesicular membranes

Homotypic fusion

81

Fusion of vesicular membrane to a organelle membrane

Heterotypic fusion

82

How are KDEL sequences recognized for retrograde transport?

Golgi membrane bound receptor

83

Motif for membrane bound residents that end up in the wrong place

KKXX

84

What is KKXX recognized by?

COPI coat machinery

85

How do KDEL receptors know when to unbind to its cargo?

Golgi is more acidic than ER, so releases in the more neutral environment of the ER

86

4 functions of golgi

Glycosylation, production of proteoglycans, protein sorting, sulfation

87

Specifically, what kind of glycosylation occurs in the golgi?

Modification of existing N-linked sugar, O-linked glycoslyation

88

4 functions of protein glycosylation

Aid in protein folding, surface coating, specific interactions, ECM

89

How does surface coating of glycosylated proteins help the protein

Protection from extracellular enivornment

90

2 classes of N-linked sugars

High mannose, complex

91

Where are high mannose sugars added?

ER

92

Where are complex sugars trimmed?

Golgi

93

What modifies complex sugars?

Glycosyltransferases

94

Example of a sugar with a negative charge

Sialic acid

95

What residues does o-linked sugar modification take place on?

Serine or threonine hydryoxyl residues

96

Primary degradative organelle of the cell

Lysosomes

97

Besides degradation, what other role does lysosomes play

Osmolyte storage

98

Role of vacuoles in a plant

OSmotic stability or turgor pressure

99

Sorting signal of proteins of secretory pathway to lysosomes

Mannose-6-phosphate sorting signal

100

What kind of singal is the Mannose-6-phosphate signal?

Signal patch

101

What is the mannose-6-phosphate sorting signal recognized by?

N-acetylglucosamine (GlcNAc) phosphotransferase in the cis-Golgi

102

How does GlcNAc-P work?

Binds high mannose and a UDP-GlcNAc and catalyzes transfer of GlcNAc phosphate to terminal mannose residue

103

How are GlcNAc sugars removed?

Glycosidase

104

What is the mannose 6-P tag recognized by?

Mannose 6-phosphate receptor (M6PR) in TGN

105

How are lysosome proteins released into the lysosome?

pH sensitivity (lysosome very acidic)