Conformation and absolute configuration of β-methyllanthionine

BIOCHEMICAL

Vol. 53, No. 2, 1973

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

CONFORMATION AND ABSOLUTE CONFIGUP,ATION OF @-METHYLLANTHIONINE J. R. Knox and P. C. Keck Eiological Sciences Group and Institute University of Connecticut, Storrs, Received

June.

6,

of Materials Connecticut,

Science 06268

1973

Summary. If the bicyclic peptide ring proposed by Gross --et al. (1,2) does in fact exist in nisin and related antibiotics. then the unusual B-methvllanthionine component must be significantly-distorted from its confo&ation in the free state, as determined by x-ray structure analysis. The torsion angles about the S-C bonds are 50-100" from the torsion angles in models of the sulfur-bridged pgptide ring proposed for nisin. The chirality of the methylated B-carbon atom is (S). The conformation of the amino acid differs from that 06 meso-lanthionine only by a 180' rotation of a carboxyl group about the C .-c,(CH,) bond. Nisin bacillus

and subtilin, subtilis,

each contain

residue

of lanthionine

function

as sulfide

three Two of

unsaturated four

(3,4).

are

these

13-atom

to form

the smallest rings

from

residues

of B-methyllanthionine

At least

bridges

of which

peptides

share

Streptococcus

lactis

in the case of nisin,

five

loops

and one these

in the peptide

heterodetic

rings

a peptide

linkage

yet

found

and

residues

chain

(1,2),

in peptides.

in a bicyclic

structure

as shown. CH3 I CH-CO-NH-C’H-CH-S
CO

co

NH

r;lH I co /

*CO-NH-C’H-FH-S,-CH,-CH-CO-NH-CH I CH,

The bridge-head

a-carbon

reported

to have

of the

configuration

the D configuration of both

B-methyllanthionine, conformation in another

with ring

atom in each a-aminobutyric (2,5).

~1- and B-carbon

aba-S-ala.

of m-lanthionine

in nisin,

followed

Copyight @ 1973 b-v Academic Press, 1~. All rights of’ reproduction irl any form reserved.

He report atoms

A comparison

that

residue

an x-ray

in the

by a comparison

ala-S-ala, with

(aba)

fragment

fragment's

which model

is

determination

hydrolysis

is made of the (6),

567

acid

nisin

is

present structures.

Vol.53,No.2,1973

BIOCHEMICAL

.Fig. 1. Comparison B-methyllanthionine indicate configuration Results

further

is

Therefore

(S).

We have confirmed

to the a-carbon

and find

threonine

(9),

that

in the methylated (8)

have

undergone

Available

lanthionine

(9)

suggests

about

sulfhydryl

group

from

L-cysteine

farther

could

chain

of the D

of the molecule, B-carbon

occur

biosynthesis during

unsaturated

towards

atom

L(a),

of configuration

on the

to the

down the

half

the methylated

a change

this

(2,5)

of B-methyllanthionine,

evidence

that

(left) and shown. Letters

the assignment

one of the precursors

c1 and B positions.

dehydroalanine

atom

the chirality

must

RESEARCH COMMUNICATIONS

of conformations of meso-lanthionine (right). Hydrogen atoms are not of a-carbon atoms.

and Discussion.

configuration

AND BIOPHYSICAL

at both

R(B)the

of B-methyl-

the addition intermediate

the amino

of a B-methyl-

terminus.

H 3

The two molecu'les equivalent arises if

within only

torsional

lanthionine forces

in

This

12". part

angles (6)

in the asymmetric

(Fig.

in determining

from are

conformational

the similarity compared

with

1 and Table

l),

the

unit

innermost

have torsion similarity

of their those

the added torsion

of the

crystal

of the

related

is

which

are

two molecules

environments.

importance

angles

angles

amino

acid

For meso-

of intramolecular

suggested

by the

BIOCHEMICAL

Vol. 53, No. 2, 1973

AND BlOPHYSlCAL

RESEARCH COMMUNICATIONS

Table 1. Selected and peptide model bond superposed in handed rotation of position.

torsional angles in meso-lanthionine, B-methyllanthionine, Zero of angleis defined with front and rear (Fig. 2). pro,iection down middle bond, Angle is positive if righteither front or rear bond is required for their super-

Torsion

Lanthionine

angle

B-Methyllanthionine Molecule 1 Flolecule

c5-sc$

-85

-88

-86

C5-SC5-Ca ;

-99

-98

-100

s-c&-c

-178

-171

-176

s-c&c

-178

59

110

-170

-170

rd$-0

33

-20

-8

Ii-tic-0 $

equivalence

in

sulfur.

nitrogen

atom substituted

nitrogen

the two amino

more on local

acids

by Gross --et al. the five of the

study

(1,2).

carbonyl

from

nine.

One of these

models

angles

can be contrasted

between

is with

zwitterion

but

at

angles torsions

models

least

torsion

shown

180

140*

t

20

-140+

involving about

in Fig.

atoms

the Ca-C bond

peptide

proposed

by the

location

of

on one side

or the

other

one S-CB torsion observed

angle

which

in B-methyllanthio-

2, and seven

seen in

change

nisin defined

angles

the angles

known how much of this

of its

torsion

acid

(Table

the amino

is due to electrostatic

of nisin rather

with

has been correlated the

presence

not with

in the antibiotic

569

ion

1).

differences

and peptide.

The activity capacity,

180

oxygen.

the

atoms and two sulfur

(~100~)

not

ring,

molecules,

32 peptide

appreciably

is

bicyclic

Of the

oxygen

for

was made of the bicyclic

contained

It

90

forces.

all

differs

90

oxygen.

of the respective

three

crystal

A conformational

for

atom substituted

At the ends of all

depend

180

8

-40" if peptide variable 40' if peptide

-160

170

Gl

--

II

150

-170

ct13-c5ca-cG

*

Nisin Peptide Bridge I Bridge

2

binding

of three

a,~

Vol. 53, No. 2, 1973

BIOCHEMICAL

AND BIOPHYSICAL

RESEARCH COMMUNICATIONS

of the bicyclic peptide fragment Fig. 2. CPK model of a conformer (residues 23 to 28) proposed to exist in nisin. Approximate torsional angles measured from this model are given in Table 1. Chemical formula is shown in text. unsaturated

side

essential the which

more

array

around

models

than

In agreement possible

two carbonyl

groups

with

sulfhydryl this,

could c

compounds

we find

to visualize

B-methyllanthionine

that

a bicyclic

form

showed

a monoclinic The space

and eight

molecules

with

a diffractometer

using

1567

intensities error

from

of the U. S. Department

i and B = 91.1".

standard

can intercept

in

none of

ionophore

an acceptable

in

coordination

a cation.

Alderton

photographs

is

which

it

5 mg of

Ilethods.

thionine

(lo),

to the organism.

32 peptide

Gordon

chains

unit group

cell

was supplied

of Agriculture

(5).

with

is

P21 with

of water

in the

graphite

background

d = 11.12, four cell.

counts

count.

570

b = 16.37,

X-ray

The structure

2 = 6.78

of B-methyllandata

copper greater

by Dr.

Diffraction

molecules

monochromatized

had background-corrected in the

subtilin

than

were

collected

KCYradiation. three

was solved

times by direct

the

BIOCHEMICAL

Vol. 53, No. 2, 1973

methods thirty

using cycles

phase

set

map which from

the

least-squares

with

a multiple

solution

of refinement an R(Karle)

revealed anomalous

the

tangent

including index

formula

RESEARCH COMMUNICATIONS

procedure

the 225 reflections

(7)

equal

two molecules.

scattering

methods,

AND BIOPHYSICAL

0.23

Absolute

of sulfur.

and the current

with

After jE[ 21.5,

was used to calculate configuration

The structure residual

(7).

the

an E

was determined

is being

refined

by

is 0.112.

REFERENCES 1. 2. 3. 4. 5. ;: 8. 9. 10.

J. L., J. Amer. Chem. Sot. 92, 2919 (1970). Gross, E., and lilorell, J. L., ibid. 3, 4634 (1971r Gross, E., and rlorell, Newton, G. G. F., Abrahm,E. Pzand Berridge, II. J., Nature 171, GO6 (1953). Gross, E., Morell, J. L., and Craig, L. C., Biochemistry 62-, 952 ( 1969). Alderton, G., J. Amer. Chem. Sot. 75, 2391 (1953). Rosenfield, R. E., and Parthasarathy, R., Acta Cryst. AZ, S-39 (1 972). Drew, M. G. E., Templeton, El. H., and Zalkin, A., Acta Cryst. Bg, 261 (1969). IUPAC-IUB Commission on Biochemical Nomenclature, Biochem. J. -'121 577 (1971). Ingram, L. C., Biochim. Biophys. Acta 184, 216 (1369). Gross, E., and Morell, J. L., J. Amer. Chem. Sot. 89-, 2791 (1967).

571