• Flavodoxins are electron-transfer proteins involved in a variety of photosynthetic and non-photosynthetic reactions

• The redox activity of flavodoxin derives from its bound flavin mononucleotide cofactor (FMN), whose intrinsic properties are profoundly modified by the host protein.

• In the last decade of flavodoxin research, the following has been revealed:o the folding pathwayo the structure and stability of the apoprotein, o the mechanism of FMN recognition, o the interactions that stabilize the functional complex and

tailor the redox potentialso many details of the binding and electron transfer to partner

proteins

Predicting the flavodoxin secondary and tertairy structure

• The next decade should witness an even deeper understanding of the flavodoxin molecule and a greater comprehension of its many physiological roles.

• The fact that flavodoxin is essential for the survival of some human pathogens could make it a drug target on its own.

Predicting the flavodoxin secondary and tertairy structure

Predicting the flavodoxin secondary and tertairy structure

• Predict using a multiple alignment of 13 flavodoxin sequences• Redox protein • Involved in photosynthesis and other crucial processes

• The 14th sequence on the bottom of the alignment is a VERY distantly related protein cheY• Chemotaxis protein• For example, it interacts with proteins at the base of the

flagellar apparatus of E. coli and promotes clockwise flagellar rotation

Flavodoxin-cheY multiple sequence alignment:

1fx1 -PKALIVYGSTTGNT-EYTAETIARQLANAG-YEVDSRDAASVEAGGLFEGFDLVLLGCSTWGDDSI------ELQDDFIPLF-DSLEETGAQGRKVACF

FLAV_DESDE MSKVLIVFGSSTGNT-ESIaQKLEELIAAGG-HEVTLLNAADASAENLADGYDAVLFgCSAWGMEDL------EMQDDFLSLF-EEFNRFGLAGRKVAAf

FLAV_DESVH MPKALIVYGSTTGNT-EYTaETIARELADAG-YEVDSRDAASVEAGGLFEGFDLVLLgCSTWGDDSI------ELQDDFIPLF-DSLEETGAQGRKVACf

FLAV_DESSA MSKSLIVYGSTTGNT-ETAaEYVAEAFENKE-IDVELKNVTDVSVADLGNGYDIVLFgCSTWGEEEI------ELQDDFIPLY-DSLENADLKGKKVSVf

FLAV_DESGI MPKALIVYGSTTGNT-EGVaEAIAKTLNSEG-METTVVNVADVTAPGLAEGYDVVLLgCSTWGDDEI------ELQEDFVPLY-EDLDRAGLKDKKVGVf

2fcr --KIGIFFSTSTGNT-TEVADFIGKTLGA---KADAPIDVDDVTDPQALKDYDLLFLGAPTWNTG----ADTERSGTSWDEFLYDKLPEVDMKDLPVAIF

FLAV_AZOVI -AKIGLFFGSNTGKT-RKVaKSIKKRFDDET-MSDA-LNVNRVS-AEDFAQYQFLILgTPTLGEGELPGLSSDCENESWEEFL-PKIEGLDFSGKTVALf

FLAV_ENTAG MATIGIFFGSDTGQT-RKVaKLIHQKLDG---IADAPLDVRRAT-REQFLSYPVLLLgTPTLGDGELPGVEAGSQYDSWQEFT-NTLSEADLTGKTVALf

FLAV_ANASP SKKIGLFYGTQTGKT-ESVaEIIRDEFGN---DVVTLHDVSQAE-VTDLNDYQYLIIgCPTWNIGEL--------QSDWEGLY-SELDDVDFNGKLVAYf

FLAV_ECOLI -AITGIFFGSDTGNT-ENIaKMIQKQLGK---DVADVHDIAKSS-KEDLEAYDILLLgIPTWYYGE--------AQCDWDDFF-PTLEEIDFNGKLVALf

4fxn -MK--IVYWSGTGNT-EKMAELIAKGIIESG-KDVNTINVSDVNIDELL-NEDILILGCSAMGDEVL-------EESEFEPFI-EEIS-TKISGKKVALF

FLAV_MEGEL MVE--IVYWSGTGNT-EAMaNEIEAAVKAAG-ADVESVRFEDTNVDDVA-SKDVILLgCPAMGSEEL-------EDSVVEPFF-TDLA-PKLKGKKVGLf

FLAV_CLOAB -MKISILYSSKTGKT-ERVaKLIEEGVKRSGNIEVKTMNLDAVD-KKFLQESEGIIFgTPTYYAN---------ISWEMKKWI-DESSEFNLEGKLGAAf

3chy ADKELKFLVVDDFSTMRRIVRNLLKELGFN--NVEEAEDGVDALNKLQAGGYGFVI---SDWNMPNM----------DGLELL-KTIRADGAMSALPVLM

T1fx1 GCGDS-SY-EYFCGA-VDAIEEKLKNLGAEIVQD---------------------GLRIDGD--PRAARDDIVGWAHDVRGAI--------

FLAV_DESDE ASGDQ-EY-EHFCGA-VPAIEERAKELgATIIAE---------------------GLKMEGD--ASNDPEAVASfAEDVLKQL--------

FLAV_DESVH GCGDS-SY-EYFCGA-VDAIEEKLKNLgAEIVQD---------------------GLRIDGD--PRAARDDIVGwAHDVRGAI--------

FLAV_DESSA GCGDS-DY-TYFCGA-VDAIEEKLEKMgAVVIGD---------------------SLKIDGD--PE--RDEIVSwGSGIADKI--------

FLAV_DESGI GCGDS-SY-TYFCGA-VDVIEKKAEELgATLVAS---------------------SLKIDGE--PD--SAEVLDwAREVLARV--------

2fcr GLGDAEGYPDNFCDA-IEEIHDCFAKQGAKPVGFSNPDDYDYEESKS-VRDGKFLGLPLDMVNDQIPMEKRVAGWVEAVVSETGV------

FLAV_AZOVI GLGDQVGYPENYLDA-LGELYSFFKDRgAKIVGSWSTDGYEFESSEA-VVDGKFVGLALDLDNQSGKTDERVAAwLAQIAPEFGLS--L--

FLAV_ENTAG GLGDQLNYSKNFVSA-MRILYDLVIARgACVVGNWPREGYKFSFSAALLENNEFVGLPLDQENQYDLTEERIDSwLEKLKPAV-L------

FLAV_ANASP GTGDQIGYADNFQDA-IGILEEKISQRgGKTVGYWSTDGYDFNDSKA-LRNGKFVGLALDEDNQSDLTDDRIKSwVAQLKSEFGL------

FLAV_ECOLI GCGDQEDYAEYFCDA-LGTIRDIIEPRgATIVGHWPTAGYHFEASKGLADDDHFVGLAIDEDRQPELTAERVEKwVKQISEELHLDEILNA

4fxn G-----SY-GWGDGKWMRDFEERMNGYGCVVVET---------------------PLIVQNE--PDEAEQDCIEFGKKIANI---------

FLAV_MEGEL G-----SY-GWGSGEWMDAWKQRTEDTgATVIGT----------------------AIVNEM--PDNA-PECKElGEAAAKA---------

FLAV_CLOAB STANSIAGGSDIA---LLTILNHLMVKgMLVYSG----GVAFGKPKTHLGYVHINEIQENEDENARIfGERiANkVKQIF-----------

3chy VTAEAKK--ENIIAA---------AQAGAS-------------------------GYVV-----KPFTAATLEEKLNKIFEKLGM------

GIteration 0 SP= 136944.00 AvSP= 10.675 SId= 4009 AvSId= 0.313

Rules of thumb when looking at a multiple alignment (MA)

• Hydrophobic residues are internal

• Gly (Thr, Ser) in loops

• MA: hydrophobic block -> internal -strand

• MA: alternating (1-1) hydrophobic/hydrophilic => edge -strand

• MA: alternating 2-2 (or 3-1) periodicity => -helix

• MA: gaps in loops

• MA: Conserved column => functional? => active site

Rules of thumb when looking at a multiple alignment (MA) … cont.

• Active site residues are together in 3D structure

• Helices often cover up core of strands

• Helices less extended than strands => more residues to cross protein

-- motif is right-handed in >95% of cases (with parallel strands)

• MA: ‘inconsistent’ alignment columns and match errors!

• Secondary structures have local anomalies, e.g. -bulges

Amino acid properties

Amino acid hydrophobicity scale

hydrophobic

hydrophilic

Burried and Edge strands

Parallel -sheet

Anti-parallel -sheet

Periodicity patterns within secondary structures

Burried -strand

Edge -strand

-helix

= hydrophilic = hydrophobic

TOPS diagrams

Circle = helix

Triangle = strand

-- motif is right-handed in >95% of cases

RH LH

Building flavodoxin

RH