PMID- 16475799
OWN - NLM
STAT- MEDLINE
DCOM- 20060410
LR  - 20071114
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 45
IP  - 7
DP  - 2006 Feb 21
TI  - Design of a minimal polypeptide unit for bacteriochlorophyll binding and 
      self-assembly based on photosynthetic bacterial light-harvesting proteins.
PG  - 2103-13
AB  - We introduce LH1beta24, a minimal 24 amino acid polypeptide that binds and 
      assembles bacteriochlorophylls (BChls) in micelles of octyl beta-glucoside (OG) 
      into complexes with spectral properties that resemble those of B820, a universal 
      intermediate in the assembly of native purple bacterial light-harvesting 
      complexes (LHs). LH1beta24 was designed by a survey of sequences and crystal 
      structures of bacterial LH proteins from different organisms combined with 
      currently available information from in vitro reconstitution studies and 
      genetically modified LHs in vivo. We took as a template for the design sphbeta31, 
      a truncated 31 amino acid analogue of the native beta-apoprotein from the core LH 
      complex of Rhodobacter sphaeroides. This peptide self-assembles with BChls to 
      form B820 and, upon cooling and lowering OG concentration, forms red-shifted B850 
      spectral species that are considered analogous to native LH complexes. We find 
      that LH1beta24 self-assembles with BChl in OG to form homodimeric B820-type 
      subunits comprising two LH1beta24 and two BChl molecules per subunit. We 
      demonstrate, by modeling the structure using the highly homologous structure of 
      LH2 from Rhodospirillum molischianum, that it has the minimal size for BChl 
      binding. Additionally, we have compared the self-assembly of sphbeta31 and 
      LH1beta24 with BChls and discovered that the association enthalpies and entropies 
      of both species are similar to those measured for native LH1 from Rhodospirillum 
      rubrum. However, sphbeta31 readily aggregates into intermediate higher oligomeric 
      species and further to form B850 species; moreover, the assembly process of these 
      oligomers is not reversible, and they are apparently large nonspecific 
      BChl-peptide coaggregates rather than well-defined nativelike LH complexes. 
      Similar aggregates were observed during LH1beta24 assembly, but these were formed 
      less readily and required lower temperatures than sphbeta31. In view of these 
      results, we reevaluate previous in vitro reconstitution studies and propose 
      alternative templates for new designs.
FAU - Noy, Dror
AU  - Noy D
AD  - Johnson Research Foundation, Department of Biochemistry and Biophysics, 
      University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. 
      dror.noy@weizmann.ac.il
FAU - Dutton, P Leslie
AU  - Dutton PL
LA  - eng
GR  - GM48130/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Bacteriochlorophylls)
RN  - 0 (Light-Harvesting Protein Complexes)
RN  - 0 (Photosystem I Protein Complex)
SB  - IM
MH  - Amino Acid Sequence
MH  - Bacteriochlorophylls/*metabolism
MH  - Centrifugation
MH  - Circular Dichroism
MH  - Light-Harvesting Protein Complexes/*metabolism
MH  - Molecular Sequence Data
MH  - Photosystem I Protein Complex/metabolism
MH  - Protein Engineering/methods
MH  - Sequence Alignment
MH  - Spectrophotometry
MH  - Thermodynamics
EDAT- 2006/02/16 09:00
MHDA- 2006/04/11 09:00
CRDT- 2006/02/16 09:00
PHST- 2006/02/16 09:00 [pubmed]
PHST- 2006/04/11 09:00 [medline]
PHST- 2006/02/16 09:00 [entrez]
AID - 10.1021/bi052175x [doi]
PST - ppublish
SO  - Biochemistry. 2006 Feb 21;45(7):2103-13. doi: 10.1021/bi052175x.