The following details were determined for one of three sac wall proteins. Analys

ID: 47693 • Letter: T

Question

The following details were determined for one of three sac wall proteins. Analyses were done on native, denatured and fragmented protein:

i. Average mass of isolated native precursor: 44,507Da by ESI

ii. Average mass of reduced protein alkylated with ethylene imine: 15,867.77Da

iii. N-terminus (edman) EASPC(modified)

iv. Purified precursor digested with collagenase following reduction and ethyleneimine alkylation: fragment A 4684.77, fragment B 7059.1 (both average mass).

v. No peptide mapping was possible, but a number of hydrolytic treaments produced some fragments with useful sequence following CID.

One fragment is a highly nodified peptide released after treating mercaptoethanol0reduced capsules with CNBr: [M+2H]2+=858.88 monoisotopic

y" ions: 1659.74, 1562.69, 1449.64, 1392.62, 1279.53, 1166.48, 1109.45, 1006.44, 850.35, 793.33, 646.26, 533.21

b ions: 1615.71, 1512.70, 1455.68, 1342.63, 1241.58, 1184.56, 1071.51

C-ladder Aminoethylated tryptic peptide (m/z 1658.83 monoisotopic): Ladder: m/z11512.76, m/z2 1413.69, m/z3 1316.64, m/z4 1185.60, m/z51088.55, m/z6 975.46, m/z7 878.41, m/z8 747.38, m/z9 650.32

a. What partial sequences can be deduced from these data?

b. What kinds of structural motifs are suggested?

Explanation / Answer

Based on the given data,

The mass of the native precursor is 44,507Da

Average mass after alkylation: 15,867.77Da

It is digested with collagenase enzyme, gives

A: 4684.77 Da

B: 7059.1Da

The peptide A has 12 sites for CNBr degradation.

The peptide B has 7 sites for CNBr degradation.

a) The partial sequence can be deduced from these data is (Da):

1659.74

1615.71

1562.69

1512.7

1449.64

1455.68

1392.62

1342.63

1279.53

1241.58

1166.48

1184.56

1109.45

1071.51

1006.44

850.35

793.33

646.26

533.21