Part:BBa_K4990007

HlpA

Usage in short

You can use it to target coloretal cancer!

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 231
  
• 1000
  COMPATIBLE WITH RFC[1000]

What you need to know!

In 2006, Tjalsma employed the Highly accurate tandem MS method to identify a protein named Histone-like protein A (HlpA). This discovery highlighted a bridge between Streptococcus bovis and colorectal cancer. It is postulated that S. bovis establishes a bond with colorectal cancer cell surfaces via heparan sulfate-proteoglycans (HSPG) mediated by HlpA [1].

By 2009, Boleij confirmed that Streptococcus gallolyticus binds to the surface of colorectal cancer cells through HlpA interacting with HSPG [2].

In 2016, O'Neil unveiled the crystal structure of Hlp, revealing its crab-claw-like architecture. The claw section's basic amino acids can bind with DNA and simultaneously with heparin [3].

In 2018, Chun Loong Ho harnessed the binding of HlpA to HSPG to construct an engineered Escherichia coli that specifically targets colorectal cancer, thus marking the commencement of the HlpA targeting system [4].

In 2022, the iGEM22_LZU-CHINA team, utilizing synthetic biology, developed an Escherichia coli that targets colorectal cancer, employing the method of HlpA targeting tumor cell surface HSPG [5].

By 2023, Tang engineered a probiotic using HlpA targeting and Azurin-induced cytotoxicity, demonstrating promising therapeutic efficacy in colorectal cancer mice models [6].

Figure A:Crystal structure of HlpA(O'Neil 2016) Figure B:Engineered EcN treat CRC(Chun 2018)

HlpA, as suggested by its name "Histone-like protein A", binds to DNA similar to histones. Its overall morphology resembles a crab claw, allowing it to non-specifically and tightly bind to the minor groove of DNA using its ribbon-like β-fold region. This results in significant DNA bending, DNA compaction, and negative supercoiling. S. bovis, through an unknown mechanism, secretes it extracellularly, acting as an anchorless protein. It becomes a target for the humoral immune system during infections. By linking bacterial lipoteichoic acid (LTA) and HSPG on colon epithelial cells, it mediates bacterial adhesion to colon tumor cells.

Therefore, HlpA possesses dual capabilities: 1. Targeting colorectal cancer and 2. Non-specifically binding to DNA chains.

What is it?

Here is the structure of HlpA monomer and homodimer.

Two helical segments from each monomeric subunit constitute an α-helical ‘body’ with two protruding β-ribbon ‘arms’ , which extend to bind the DNA helix. These DNA-binding β-ribbons are largely disordered in the absence of DNA.

What can it do?

HlpA单体被用于设计融合蛋白，它可以与结直肠癌细胞表面的HSPG进行结合。因此，如果你想用蛋白靶向结直肠癌细胞，你就可以设计一个融合蛋白，将HlpA挂在融合蛋白的一端。如果你想让细胞靶向结直肠癌细胞，则可以为你的底盘细胞量身定制一种包含HlpA的膜蛋白，通过表面展示技术将HlpA表达在地盘细胞表面，它就可以用于靶向结直肠癌细胞[4-6]。

除此之外，HlpA类似于大肠杆菌的HU蛋白。大肠杆菌HU异源二聚体与双链DNA非特异性结合，与结构扭曲的DNA具有更高的亲和力，从而导致显著的DNA弯曲、DNA压实和负超螺旋的形成。HlpA与DNA的结合具有非特异性的，并且对富含AT的DNA具有偏好性[3]。

最后，不得不提到的是，这些HlpA单体可以自组装为同源二聚体，它们之间的结合具有巨大的亲和力。因此，在我们的双靶向肽相关实验中，观察到了显著的二聚化现象。

How does it work?

Examination of the DNA-binding region of Hlp revealed that this area is primarily composed of positively charged residues that form a pocket to accommodate DNA binding. The specific residues that comprise the DNA-binding pocket are depicted in Figure below. It should be noted that the side-chain electron density for Arg56, Lys60, Lys71 and Lys73 of subunit A and Arg54, Lys76 and Lys81 of subunit B was partially disordered and could not be traced in the electrondensity maps. Therefore, the side chains were modeled in idealized rotamer positions for the electrostatic surface calculations.[3]

Referrence

[1]Tjalsma H, Schöller‐Guinard M, Lasonder E, et al. Profiling the humoral immune response in colon cancer patients: diagnostic antigens from Streptococcus bovis[J]. International journal of cancer, 2006, 119(9): 2127-2135.

[2]Boleij A, Schaeps R M J, de Kleijn S, et al. Surface-exposed histone-like protein a modulates adherence of Streptococcus gallolyticus to colon adenocarcinoma cells[J]. Infection and immunity, 2009, 77(12): 5519-5527.

[3]O'Neil P, Lovell S, Mehzabeen N, et al. Crystal structure of histone-like protein from Streptococcus mutans refined to 1.9 Å resolution[J]. Acta Crystallographica Section F: Structural Biology Communications, 2016, 72(4): 257-262.

[4]Ho C L, Tan H Q, Chua K J, et al. Engineered commensal microbes for diet-mediated colorectal-cancer chemoprevention[J]. Nature biomedical engineering, 2018, 2(1): 27-37.

[5]https://2022.igem.wiki/lzu-china/

[6]Tang, H., Zhou, T., Jin, W., Zong, S., Mamtimin, T., Salama, E. S., ... & Li, X. (2023). Tumor-targeting engineered probiotic Escherichia coli Nissle 1917 inhibits colorectal tumorigenesis and modulates gut microbiota homeostasis in mice. Life Sciences, 324, 121709.